i卡會員

Whilst the commercial deployment of 5G is yet to become prevalent around the world, and the research and standardization of 6G are still underway, leading countries in communications technology have come up with their own visions for 6G. The potential 6G technologies can be developed along two paths. The first is an evolution based on 5G, incorporating artificial intelligence, next-generation MIMO (multiple-input, multiple-output) and mmWaves (millimeter waves). The other involves the exploration of emerging technologies such as terahertz (THz) communications, Reconfigurable Intelligent Surface (RIS), and non-terrestrial networks. Although the developmental path and application scenarios of 6G technologies are not yet determined, the increase in transmission rates and the expansion of spectrums have already become the contested ground for industry players.

Increase in transmission rates and expansion of spectrums as the priorities for 6G technologies

It is generally expected that 6G will focus on the terahertz (THz) frequency band. The terahertz frequency range is from 0.1 to 10 THz, corresponding to electromagnetic wavelengths from 3 mm to 30 μm, which is between microwaves and visible light.

The 100 to 300 GHz frequency band is referred to as sub-terahertz (sub-THz). Tech heavyweights Samsung and LG from South Korea, and Nokia of Finland have made breakthroughs in terahertz component technologies. Moreover, the U.S. Federal Communications Commission (FCC) opened up the high-frequency bands between 95 GHz and 3 THz in 2019 for experimental use. Given the breakthroughs in terahertz technology and the opening up of frequency spectrums, more research resources are expected to be invested in this area.

The applications of terahertz in 6G can be divided into two main categories. One is fixed point-to-point communication applications, such as high-capacity wireless access and backhaul. The other is mobile communication and sensing applications, such as immersive experiences, integrated sensing and communication, etc. This shows that the transmission distance of terahertz applications ranges from less than 1 meter to over 100 meters.

According to the white paper published by Samsung in 2022, 6G should cover the low, medium, and high frequency bands below 300 GHz (the sub-terahertz range). The Next G Alliance in the U.S. and the Hexa-X project in the European Union share the same view. None of the terahertz frequency spectrum from 300 GHz to 3 THz is currently the focus of 6G development. Most of the discussions at this stage are on the W band (92-115 GHz) and the D band (130-175 GHz). The W band has a lower wavelength and better propagation characteristics. However, the ITU-RR (Radio Regulations) limits its ability to provide a continuous bandwidth greater than 10 GHz. The D band has slightly poorer propagation characteristics than the W band, but can provide continuous bandwidths in the order of tens of GHz. Hence, the D band is the focus of attention for major international companies.

The key components for 6G terahertz communications, such as digital signal processors (DSPs), digital-to-analog converters (DACs), and analog-to-digital converters (ADCs) will be primarily manufactured with advanced CMOS processes. The main technical challenges will be IC design, manufacturing, testing and packaging. As for power amplifiers (PAs) for 6G terahertz development, there are multiple approaches and solutions, and it is still unclear which technology will be adopted in the future. It will therefore be necessary to keep an eye on the trends of technological development.

The 6G Smart Networks and Services Industry Association (6G-IA) is still in the early stages of evaluation and R&D for the various sub-terahertz PA (power amplifier) technologies for 6G. The Next G Alliance in North America believes that silicon-germanium (SiGe) and indium phosphide (InP) have the potential to achieve the production costs and scale required for mass production of sub-terahertz PAs. Currently, the US Defense Advanced Research Projects Agency (DARPA) has a specific program to support research and development in this area. The Hexa-X project in the European Union emphasizes CMOS, SiGe BiCMOS, and InP as the three core technologies for sub-terahertz PAs.

In response to the future development of terahertz, new startups have emerged globally: TeraView, a British startup founded in April 2001, has been developing non-invasive and non-destructive inspection for the terahertz spectrum, including fault analysis for communication semiconductor chips, as well as non-destructive testing in the automotive, pharmaceutical, and cultural heritage fields. The American startup RaySecur provides remote analysis and other detection solutions via terahertz scanning with its 4D dynamic desktop terahertz mail scanner. The French startup TiHive Technologies has developed miniaturized terahertz imaging systems that utilize machine learning and provide non-contact solutions for quality control and optimization of raw materials usage for multiple industries.

Whilst startups have made inroads, Taiwanese companies have an advantage in information and communication technology

Given its robust structure and scale of the information, communication and telecommunication industry, Taiwan commands an advantageous position in terahertz development. In the future, Taiwan can venture into both communications and non-communication fields of 6G terahertz, from applications such as high-capacity wireless communications, data center networks and short-range communications, or by focusing on non-destructive testing, security inspection and pharmaceutical inspection, etc. It is foreseeable that terahertz development will make tremendous progress in the next decade. Taiwan needs an overarching plan for the development of key terahertz technologies and its key components in order to seize opportunities in the 6G terahertz communications and non-communication application markets.