Towards More Efficient Wireless Power Transfer for 6G

Abstract

As time is moving forward, the world is becoming more dependent on Internet of Things (IoT) devices. The vision for the future involves IoT devices participating in various aspects of our daily lives, including sensing, controlling, and communicating. Such a future requires a significant number of IoT devices, which raises questions regarding sustainability in terms of battery waste. One promising candidate technology for providing power to IoT devices is Wireless Power Transfer (WPT). WPT can provide a convenient way of powering devices wirelessly, which decreases the need to use batteries.

It is known that the efficiency of a WPT system is highly dependent on the waveform used for power transmission, hence it is highly desirable to find waveform designs that enhance the end-to-end efficiency of WPT. In this work, our goal is to find waveforms that maximize the harvested power at the receiver of the WPT system, for a large number of transmitting antennas. We do this by developing a simulation framework using MATLAB, where we can do fast simulations for various system parameters, while taking into consideration the full characteristics of the WPT system.

Through our results we concluded that using Maximum Ratio Transmission is a viable waveform design strategy with low complexity. Using a larger number of antennas decreases the distortion caused by the amplifiers at the transmitter and increases the received power. Moreover, due to the receivers non-linearity, for a certain average power, having a waveform with a higher Peak to Average Power Ratio (PAPR) enhances the end-to-end WPT efficiency. However, this is only true up to a certain limit that depends on the rectifier circuit parameters. We also investigated several ways of deciding which subcarriers to use for transmission in the available bandwidth, and found a tone selection scheme aimed at maximizing the PAPR of the signal at the receiver while maintaining high efficiency at the transmitter with minimal distortion.

Popular Abstract

Have you ever taken a moment to reflect on how wireless communication and the dawn of the information age have transformed our world? If someone from a century ago saw what we are able to do with devices in the palms of our hands, describing their astonishment as a mere "shock" would be an understatement. Now picture a future where we harness the same ability, but with energy transfer instead of information transfer. This is precisely the idea behind the topic of Wireless Power Transfer (WPT), where radio frequency signals are used to transfer power wirelessly through space, from an energy transmitter to an energy receiver. In principle, this would allow electricity to be sent through the air, much like how your Wi-Fi sends data.

Through WPT, we could have networks that conveniently power our ever increasing Internet of Things devices without batteries, even in environments that are inaccessible for humans, allowing for a significant reduction in battery waste and contributing to a more sustainable society.

There are numerous challenges that must be tackled to materialize WPT into a feasible and widely used reality. The biggest among these challenges is enhancing the efficiency of WPT. Higher efficiency leads to a larger WPT coverage area and the possibility of using WPT in a wider range of applications. This thesis recognizes the importance of enhancing the efficiency of WPT and focuses on this very challenge, by designing signals with characteristics that lead to increased WPT efficiency. We do this through computer simulations, by tweaking several signal parameters and assessing their impact on the harvested power at the energy receiver.

Through our investigations, we noted that finding the transmit signals that optimize the efficiency is a highly computationally demanding task, especially for systems with a large number of antennas. This is a major difficulty when designing signals for WPT. Therefore, in this thesis, to avoid the computational complexity concern, we explore using a heuristic signal design approach as a way of increasing the efficiency. As a result, we end up with simulations that demonstrate the effectiveness of using the heuristic approach, even when considering the entire WPT system characteristics with a large number of antennas. We also take a close look at the challenge associated with achieving efficient power transfer while minimizing interference with other systems. To get more details, we encourage you to read this thesis.

• author: Al-Ameri, Ali and Park, Jaeyoung
• supervisor: Ove Edfors
• organization: Department of Electrical and Information Technology
• course: EITM02 20231
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• report number: LU/LTH-EIT 2023-946
• language: English
• id: 9135502
• date added to LUP: 2023-09-19 14:28:32
• date last changed: 2023-09-19 14:28:32