Researchers at Tokyo Tech have developed a groundbreaking 256-element wirelessly powered transceiver array for 5G communication, designed to address challenges like low SNR and signal blockage due to physical obstacles. This array utilizes beamforming and advanced power conversion technologies to enhance signal quality and extend network coverage, particularly in non-line-of-sight environments. By achieving significant improvements in power conversion efficiency and SNR, this transceiver array promises to expand 5G accessibility and reliability, thereby fostering more ubiquitous and effective wireless communication.

Researchers have developed an innovative wirelessly powered relay transceiver that enhances 5G network coverage, even in areas where the connection is obstructed.

Scientists at Tokyo Tech have designed an innovative 256-element wirelessly powered transceiver array for non-line-of-sight 5G communication. This novel design features efficient wireless power transmission and high-power conversion efficiency, which can enhance 5G network coverage even in areas with link blockage. The enhanced flexibility and coverage area could potentially make high-speed, low-latency communication more accessible.

Millimeter wave 5G communication, which uses extremely high-frequency radio signals (24 to 100 GHz), is a promising technology for next-generation wireless communication, exhibiting high speed, low latency, and large network capacity. However, current 5G networks face two key challenges. The first one is the low signal-to-noise ratio (SNR). A high SNR is crucial for good communication. Another challenge is link blockage, which refers to the disruption in signal between transmitter and receiver due to obstacles such as buildings.

The proposed transceiver design enables high power conversion efficiency and conversion gain, enhancing 5G network coverage even in areas with link blockage. Credit: 2024 IEEE MTT-S International Microwave Symposium

Beamforming and Non-Line-of-Sight Solutions

Beamforming is a key technique for long-distance communication using millimeter waves which improves SNR. This technique uses an array of sensors to focus radio signals into a narrow beam in a specific direction, akin to focusing a flashlight beam on a single point. However, it is limited to line-of-sight communication, where transmitters and receivers must be in a straight line, and the received signal can become degraded due to obstacles. Furthermore, concrete and modern glass materials can cause high propagation losses. Hence, there is an urgent need for a non-line-of-sight (NLoS) relay system to extend the 5G network coverage, especially indoors.

To address these issues, a team of researchers led by Associate Professor Atsushi Shirane from the Laboratory for Future Interdisciplinary Research of Science and Technology at the Tokyo Institute of Technology (Tokyo Tech) designed a novel wirelessly powered relay transceiver for 28 GHz millimeter-wave 5G communication (as shown in Figure 1). Their study has been published in the Proceedings of the 2024 IEEE MTT-S International Microwave Symposium.

The board includes gallium arsenide diodes, balun ICs, DPDT switch ICs, and digital ICs. This circuit generates DC from 24GHz WPT signal and downconverts 28GHz RF signal to 4GHz IF signal simultaneously. Credit: 2024 IEEE MTT-S International Microwave Symposium

Explaining the motivation behind their study, Shirane says, “Previously, for NLoS communication, two types of 5G relays have been explored: an active type and a wireless-powered type. While the active relay can maintain a good SNR even with few rectifier arrays, it has high power consumption. The wirelessly powered type does not require a dedicated power supply but needs many rectifier arrays to maintain SNR due to low conversion gain and uses CMOS diodes with lower than ten percent power conversion efficiency. Our design addresses their issues while using commercially available semiconductor integrated circuits (ICs).”

Technical Specifications and Testing Results

The proposed transceiver consists of 256 rectifier arrays with 24 GHz wireless power transfer (WPT). These arrays consist of discrete ICs, including gallium arsenide diodes, and baluns, which interface between balanced and unbalanced (bal–un) signal lines, DPDT switches, and digital ICs (refer Figure 2). Notably, the transceiver is capable of simultaneous data and power transmission, converting 24 GHz WPT signal to direct current (DC) and facilitating 28 GHz bi-directional transmission and reception at the same time. The 24 GHz signal is received at each rectifier individually, while the 28 GHz signal is transmitted and received using beamforming. Both signals can be received from the same or different directions and the 28 GHz signal can be transmitted either with retro-reflecting with the 24 GHz pilot signal or in any direction.

Testing revealed that the proposed transceiver can achieve a power conversion efficiency of 54% and a conversion gain of –19 decibels, higher than conventional transceivers while maintaining SNR over long distances. Additionally, it achieves about 56 milliwatts of power generation which can be increased even further by increasing the number of arrays. This can also improve the resolution of the transmission and reception beams. “The proposed transceiver can contribute to the deployment of the millimeter-wave 5G network even to places where the link is blocked, improving installation flexibility and coverage area,” remarks Shirane about the benefits of their device.

This new transceiver will make 5G networks more common, making high-speed, low-latency communication accessible to all!

Meeting: 2024 IEEE MTT-S International Microwave Symposium

The study was funded by the Ministry of Internal Affairs and Communications, the National Institute of Information and Communications Technology, and the Japan Science and Technology Agency.