SEU Achieved Progress in Information Metamaterials
[Southeast University Network, March 23] (Correspondent: Zhang Lei) Recently, Academician Cui Tiejun and Prof. Cheng Qiang's research team, from the Institute of Electromagnetic Space and State Key Laboratory of Millimeter Waves of SEU, together with Prof. Jin Shi's research team, from the National Mobile Communications Research Laboratory have achieved significant progress in the field of information metamaterials. By utilizing STC digital meta-surface, the information can be directly loaded into the characteristics on spatial and frequency spectrums of electromagnetic waves, realizing a new wireless communication mechanism that features space-division multiplexing and frequency- division multiplexing. Their research results, titled "A wireless communication scheme based on space - and frequency- division multiplexing using digital meta-surfaces", were published in the world-famous journal Nature Electronics on March 18, with Southeast University as the first undersigned institute, Academician Cui Tiejun, Prof. Cheng Qiang and Prof. Jin Shi as the corresponding authors, Dr. Zhang Lei from SEU as the first author. Meanwhile, the collaborators included Dr. Chen Mingzheng, Dr. Tang Wankai, Dr. Dai Junyan, Dr. Miao Long and teacher Zhou Xiaoyang all from SEU.
Since 2014 when the concept of "digital coding and programmable metamaterials/meta-surfaces" was proposed by Academician Cui Tiejun's research team (light: Science & Applications 3, e218, 2014), related research has been regarded as a hot topic in the global community of metamaterials. By changing the coding sequence to control the radiation or scattering characteristics of electromagnetic waves, digital meta-surfaces can simplify the design process, facilitate the simulation optimization and the processing test, and make it possible to encode and process information in physical space. What's more, the representation mode of digital coding can also establish a link between the physical world and the digital world, making it possible to study the meta-surfaces from the perspective of information science, and creating a new domain of "information metamaterials/meta-surfaces" (Journal of Materials Chemistry C 5, 3644-3668, 2017; iScence 23, 101403, 2020). The information meta-surfaces can manipulate electromagnetic waves in real time, process digital information directly, and deepen the perception, learning and recognition of information. In 2018, the concept of "spatiotemporal coded digital hypersurface" was proposed, which unified the coding of spatial domain and time domain that electromagnetic regulation and information processing can be conducted in both domains simultaneously. (Nature Communications 9, 4334, 2018), which has expanded the application of information meta-surfaces.
The current era witnesses the rapid development of the fifth generation of mobile communication technology (5g) while the research of 6G is in the ascendant. It's expected that the wireless communication will put forward higher performance requirements for radio frequency links and large-scale antenna arrays in the future, thus the industry will face numerous challenges in terms of cost, performance, power consumption, and integration etc. In the course, multiplexing technology can be widely applied for information transmission in mobile communication because with multiple independent channels established between transceivers, the capacity of communication network will be greatly improved. Among multiplexing technologies, the time-division multiplexing (TDM), the frequency-division multiplexing (FDM), the coding-division multiplexing (CDM) as well as the space-division multiplexing (SDM) have been widely adopted in mobile communication for decades. For traditional frequency-division multiplexing technology, it usually relies on high-performance filters and mixers to divide the frequency band. In addition, the traditional space-division multiplexing technology also applies multi antennas and corresponding RF components to constitute a multi-channel array transceiver, likewise resulting in high cost and complexity for the system.
Fig. 1. The space- and frequency-multiplexing wireless communication system for direct data transmissions using an STC digital meta-surfaces
To further improve the powerful control of the STC digital meta-surfaces over electromagnetic information, the researchers utilized STC digital meta-surfaces to precisely modulate the transmission direction of electromagnetic and the distribution of harmonic frequency, integrating the function of power radiance and information modulation, so as to conduct coding and digital information procession within time and space simultaneously. By optimizing the STC matrices, the information can be directly loaded onto the characteristic points on spatial spectrum and frequency spectrum, realizing a new multiplexing communication system highlighting both space-division multiplexing and frequency-division multiplexing. Based on the number and location of target users, a pre-designed direct information coding scheme was adopted, which simultaneously and independently transmitted real-time information with multiple users without the need of digital/analog conversion and mixing (as shown in Fig. 1). Besides, this approach has offered secure transmission through directional modulation, indicating undesired users located at untargeted positions cannot recover the correct information.
Fig. 2. A prototype of the dual-channel wireless communication system based on STC digital meta-surfaces, transmitting two different pictures to two users simultaneously without mutual interference.
To verify the basic theory, the researchers built a dual-channel wireless to transmit different messages to two designated users located at any position withing the space simultaneously and independently. With independent frequency channels, the system achieved low interference between different users, demonstrating the feasibility of STC program (as shown in Fig. 2). In a word, this new multiplexing wireless communication system can offer a low-cost solution with simplified structures. As a result, the need for antenna arrays, filters, mixers and other RF components, as traditionally, will be eliminated. The STC digital meta-surfaces allow a less expensive and complicated program to implement space- and frequency- division techniques. It promises a broad application prospect in newer multiplexing wireless communication and radar system in the future. A special introduction of this work titled "Meta-surfaces for multiplexed communication" was published on Nature Electronics by Prof. Shuai Nie and Prof. Ian F. Akyildiz from GIT (Nature Electronics, doi.org/10.1038/s41928-021-00555-3, 2021).
This work was supported by the significant special project titled "Theoretical System and Key Technologies of Microwave- and Millimeter-wave- Digital Coding and Field-programmable Metamaterial" in the National Key Research and Development Program "Key Issues in Revolutionary Technologies" of the Ministry of Science and Technology, the National Science Foundation of China for Distinguished Young Scholars, the National Natural Science Foundation of China, and China Postdoctoral Science Foundation etc.
The paper's link:
https://www.nature.com/articles/s41928-021-00554-4
Additional readings:
https://www.nature.com/articles/s41928-021-00555-3
https://devicematerialscommunity.nature.com/posts/metasurface-physics-helps-establish-a-new-wireless-communication-scheme
Submitted by: School of Information Science and Engineering
Editor-in-charge：Ji Hong
Reviewed by: Li Xiaonan
Translated by: Melody Zhang
Revised by: Yang Ying
Edited by: Sha Lu
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