Key electronic device developed for the massive arrival of 6G networks
The device, a telecommunications switch, is more sustainable and doubles the performance of current devices
UAB researchers were involved in the development of a switch, an essential device in telecommunications, capable of operating at very high frequency with lower power consumption than conventional technologies. The technology has applications in the new 6G mass communication systems and is more sustainable in terms of energy consumption than current devices. The study was published recently in Nature Electronics.
An indispensable element for controlling signals in electronic communication devices is the switch, whose function is to allow an electrical signal to pass (ON state) or to block it (OFF state). The fastest elements currently used to perform this function are silicon-based (the so-called RF silicon-on-insulator MOSFET switches) and operate using signals with frequencies of tens of gigahertz (GHz). However, they are volatile, i.e., they require a constant power source to maintain the ON state. To improve current communication systems and meet the demand for increasingly faster communications that will involve the Internet of Things (IoT) and the popularisation of virtual reality, it is necessary to increase the frequency of the signals with which these elements are able to act, and improve their performance.
An international collaboration involving researchers from the UAB Department of Telecommunications and Systems Engineering has developed a switch that, for the first time, is capable of performing at twice the operating frequency of current silicon-based devices, with a frequency range of up to 120 GHz, and without the need to apply a constant voltage.
The new switch uses a non-volatile material, called hBN (Hexagonal Boron Nitride), which allows its ON or OFF state to be activated by applying an electrical voltage pulse instead of a constant signal. In this way, the energy savings that can be attained are very significant.
"Our research team from the Department of Telecommunications and Systems Engineering at the UAB was involved in the design of the devices and their experimental characterisation in the laboratory," explains researcher Jordi Verdú. "For the first time we have been able to demonstrate the operation of a switch based on hBN, a non-volatile material, in a frequency range of up to 120 GHz, which suggests the possibility of using this technology in the new 6G mass communications systems, where a very high number of these elements will be required". For Verdú, this is a "very important contribution, not only from the point of view of device performance, but also towards a much more sustainable technology in terms of energy consumption".
These devices work thanks to the property of memristance, the change in electrical resistance of a material when a voltage is applied. Until now, very fast switches had been developed experimentally from memristors (devices with memristance) created with two-dimensional networks of hexagonal boron nitride (hBN) bonded together to form a surface. With this arrangement, the device frequency could reach up to 480 GHz, but only for 30 cycles, i.e., with no practical application. The new proposal uses the same material, but arranged in a superposition of layers (between 12 and 18 layers in total) that can operate at 260 GHz and with a sufficiently high stability of about 2000 cycles to be implemented in electronic devices.
The research, recently published in the journal Nature Electronics, was coordinated by the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, with the involvement of researchers from the Department of Telecommunications and Systems Engineering at the UAB Jordi Verdú, Eloi Guerrero, Lluís Acosta and Pedro de Paco, as well as researchers from the University of Texas at Austin (USA), the Tyndall National Institute and University College Cork (both in Ireland).
JOURNAL
Nature Electronics
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Memristive circuits based on multilayer hexagonal boron nitride for millimetre-wave radiofrequency applications
Pusan National University researchers propose backscatter communication technique for low-power internet of things communication
The new system is 40% more energy-efficient than conventional backscattering systems and enables integrated sensing and communication technology
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THE RESEARCHERS USED CIRCUIT MODELING, ADVANCED MODULATION TECHNIQUES, AND POLARIZATION DIVERSITY TO DESIGN A MIMO TRANSCEIVER SYSTEM FOR BACKCOM APPLICATIONS, ACHIEVING A SPECTRAL EFFICIENCY OF 2.0 BPS/HZ AND IMPROVING ENERGY EFFICIENCY BY 40% COMPARED TO CONVENTIONAL TECHNIQUES.
view moreCREDIT: PROFESSOR SANGKIL KIM FROM PUSAN NATIONAL UNIVERSITY
Backscatter communication (BackCom) is a promising low-power method for the widespread adoption of the Internet of Things (IoT) technologies, where connected devices reflect and modulate existing signals by altering their load impedance, rather than generating signals themselves. To achieve low bit error rates and high data rates, higher-order modulation schemes such as Quadrature Amplitude Modulation (QAM) are selected based on accurately modeled reflection coefficients. However, discrepancies between simulations and real-world measurements make it challenging to accurately predict the optimal reflection coefficient.
In a recent study, a research team led by Professor Sangkil Kim from the Department of Electronics Engineering at Pusan National University used transfer learning to accurately model the in-phase/quadrature or I/Q load modulators. Additionally, they introduced polarization diversity to design a BackCom system that utilizes multiple antennas for simultaneous signal transmission and reception. Their paper was made available online on 20 March 2024 and published in Volume 11, Issue 12 of the IEEE Internet of Things Journal on 15 June 2024.
“As the technology for more efficient and reliable backscatter communication improves, it lowers the barrier for IoT adoption across numerous industries. This could lead to a proliferation of IoT devices and integrated sensing and communication (ISC), facilitating smart cities, more efficient industries, and enhanced personal and public services,” says Prof. Kim.
Transfer learning involves applying knowledge gained from one task to enhance performance on a related task. The researchers pretrained an artificial neural network (ANN) using simulated input bias voltages (VI and VQ). This initial training step familiarized the ANN with the load modulator behaviors across varying voltage conditions. The knowledge gained from the pretraining step was then used in a main training step, where the ANN was trained using experimental data to predict reflection coefficients based on VI and VQ inputs.
This transfer of knowledge enabled the ANN to improve its predictions, achieving a minimal deviation of only 0.81% between modeled and measured reflection coefficients. Using these accurate models, researchers selected optimal 4- and 16-QAM schemes by aligning predicted reflection coefficients with specific points in the QAM constellation. This optimization ensured energy-efficient data transmission, with total consumption below 0.6 mW, much lower than conventional wireless systems.
Following this, the researchers designed a 2 × 2 × 2 MIMO transceiver system for BackCom, featuring two transmit and two receive antennas with different polarizations (such as vertical and horizontal). This setup enhances signal reception, throughput, and efficiency in BackCom. Utilizing a dual-polarized Vivaldi antenna, the team achieved a high gain exceeding 11.5 dBi and effective cross-polarization suppression of 18 dB.
The researchers tested their algorithm and MIMO BackCom system in the 5.725 GHz to 5.875 GHz C-band of the Industrial, Scientific, and Medical band, offering a 150 MHz bandwidth. Their approach achieved a spectral efficiency of 2.0 bps/Hz using 4-QAM modulation, demonstrating effective bandwidth utilization. They also attained an error vector magnitude of 9.35%, indicating high reliability and efficiency in data transmission.
“The combination of accurate circuit modeling, advanced modulation techniques, and polarization diversity, all tested in over-the-air environments, presents a holistic approach to tackling the challenges in ISC and IoT,” says Prof. Kim.
Overall, the proposed system lays the groundwork for a highly reliable and efficient backscatter system for multiple applications, including consumer electronics, healthcare monitoring, smart infrastructure for urban management, environmental sensing, and even radar communication.
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Reference
DOI: 10.1109/JIOT.2024.3379854
ORCID ID: 0000-0003-1720-2410
About the institute
Pusan National University, located in Busan, South Korea, was founded in 1946, and is now the no. 1 national university of South Korea in research and educational competency. The multi-campus university also has other smaller campuses in Yangsan, Miryang, and Ami. The university prides itself on the principles of truth, freedom, and service, and has approximately 30,000 students, 1200 professors, and 750 faculty members. The university is composed of 14 colleges (schools) and one independent division, with 103 departments in all.
Website: https://www.pusan.ac.kr/eng/Main.do
About the author
Prof. Sangkil Kim graduated magna cum laude with a B.S. from Yonsei University in 2010. He earned his M.S. and Ph.D. from the Georgia Institute of Technology in 2012 and 2014, respectively. From 2015 to 2018, he was the lead engineer at Qualcomm, pioneering the world’s first 5G mmWave AiP module for mobile devices. In 2018, he joined Pusan National University, where his SWARM lab focuses on advanced mmWave phased antenna arrays, machine learning-enhanced backscattering communication, and RF-photonics systems. Dr. Kim has received several accolades, including the IET Premium Award in 2015 and the KIEES Young Researcher Award in 2019. He is also a member of the IEEE MTT-26 RFID, Wireless Sensors, and IoT Committee.
JOURNAL
IEEE Internet of Things Journal
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Polarization Diversity and Transfer Learning Based Modulation Optimization for High-Speed Dual Channel MIMO Backscatter Communication
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