Terahertz wave is the electromagnetic wave with frequency range between 0.1-10thz and wavelength of 30um-3000um. The electromagnetic wave in this band is located between the microwave band and the visible light band, and the low frequency part coincides with the millimeter band. The unique characteristics of terahertz band electromagnetic wave in frequency band resources make it a key supporting technology suitable for future 6G communication. In order to play the demand traction role of operators as much as possible, accelerate and promote the development of terahertz communication technology industry chain.
Key technologies of terahertz communication
1 terahertz key device and prototype system
The research and production capacity of terahertz key devices / chips / components is the most critical core technology of terahertz communication and the biggest challenge for terahertz communication applications.
Analog link related high frequency analog discrete devices, including terahertz power amplifier, terahertz antenna, terahertz frequency multiplier, terahertz mixer, terahertz filter, terahertz low noise amplifier, etc. The research and development capability of terahertz communication key devices is close to the international leading level in China. However, in the future, the performance of the key devices in terahertz communication needs to be improved in terms of power emission capability, working environment, frequency conversion loss and power consumption. In addition, the chip integration of system link is inevitable development trend in the future, and the continuous breakthrough and progress of core technology are needed.
In addition to the integrated chip of analog link system, terahertz communication will face the technical challenges in the future in the fields of UWB digital analog to analog and analog conversion chips, digital baseband processing chips, etc. Because the available bandwidth (>2 GHz) of terahertz is much larger than the working band used by 4G and 5g systems (< 800 MHz), the current mainstream digital analog and analog-to-digital conversion chips are difficult to meet the requirements of sampling bandwidth. In addition, the processing of ultra large bandwidth signal will bring very large power consumption pressure to baseband processing chip. Therefore, on the one hand, we need to develop a higher sampling rate of large bandwidth digital analog to digital converter chip, low-power baseband processing chip; on the other hand, it is to develop low-quality signal processing system. The future implementation of terahertz communication system may require the combination of two directions to solve the problem of digital to analog conversion and baseband processing.
At present, the research and development capability of key discrete parts and prototype verification system of terahertz communication is close to the international advanced level, and the chip capacity is weak. The research results of relevant domestic directions are mainly concentrated in universities and research institutes and other institutions, with low industrial maturity. At present, the terahertz communication prototype system is mostly verified by wireless transmission capability. In the future, the capability indexes of communication distance, real-time, space division multiplexing, power consumption and cost should be considered. The breakthrough of the performance index of key core devices / chips in terahertz communication and the mature development of related industrial chain are the necessary conditions and guarantee for the above-mentioned capability.
2 terahertz propagation characteristics and channel modeling
Terahertz electromagnetic waves can easily penetrate ceramics, paper, wood, textiles and plastics, but it is difficult to penetrate metals and water. In the atmospheric environment, the high free space loss and the extra attenuation caused by atmospheric effect are a huge challenge. Under different weather conditions, such as atmospheric molecules, raindrops or fog droplets, they may cause high attenuation or scattering of terahertz band electromagnetic wave. However, in some certain terahertz window frequency bands, low attenuation can still be generated, which can be used in wireless communication transmission. Many achievements have been published on the propagation characteristics of terahertz in sunny air, rainy days, fog and other scenarioses.
There are three kinds of models, which are parametric statistical channel modeling, deterministic channel modeling and so on. The experimental results of some indoor scenes based on THz communication show that the transmission path of terahertz is sparse, and in the future, channel modeling of terahertz communication tends to use deterministic channel modeling or parameterized semi deterministic channel modeling methods, such as ray tracing method, and digital map hybrid modeling method combining deterministic and statistical characteristics.
The propagation characteristics and channel modeling of terahertz wave will directly affect the deployment of the actual application scenarioses of THz communication, which is the basic research of the application of terahertz communication. Terahertz communication may be used in multi-dimensional, macro to micro multi-scale applications of space, earth and sea in the future. The channel modeling of terahertz communication needs to explore and study the channel propagation model under different application scenarioses to be applied to the future actual scenario deployment.
3 terahertz communication air port technology
Compared with 5g air port technology, terahertz communication has the resource advantage of large bandwidth. However, the hardware link of terahertz communication prototype system also has some undesirable factors, such as large frequency conversion loss, limited sampling bandwidth, high baseband processing power consumption. In addition to the new evolution requirements in baseband waveform design, frame structure and parameter set design, modulation and coding, beam management and other technology chains, terahertz communication air port technology is also affected by the ability of terahertz communication hardware system. The algorithm design and compensation for various non ideal characteristics and factors of system link is also the technology to be considered and studied Direction.
The characteristics and advantages of ultra-high rate terahertz communication need not only the transmission ability of hardware link, but also the effective design of air port technology to ensure and realize. It includes the dynamic allocations of spectrum and bandwidth resources, intelligent management of beam access, high and low frequency, multi-dimensional space and space, macro to micro multi-scale air interface cooperation and information fusion. The future air port design scheme needs to have the above capabilities and characteristics to adapt to the technical features and advantages of 6G terahertz communication. At present, 6G technology research is still in the initial stage of exploration, and the technical route is not clear. It needs the industry to participate in the research and actively explore, and gradually clarify the future technical route and development direction of terahertz communication air port.
Terahertz communication target vision and development suggestions
In the future 6G communication, terahertz communication technology will be integrated with other low-frequency networks, which will be widely used in various ground-based ultra wideband wireless access and fiber-optic alternative scenarioses. It will carry satellites, UAVs, airships and other platforms as wireless relay equipment, which will be applied to the multi-dimensional integrated communication of space, space and sea, and the multi-scale communication from macro to micro, which will become the future social information The important supporting technology of information fusion connection. The continuous development of terahertz technology and the realization of its vision and communication technology are becoming more and more mature. The country needs to lay out ahead of time, grasp the industrial development window period in the next 5-10 years, increase support in policy support and industrial guidance, carry out tendentious layout, continuously enhance independent innovation research and development ability and core competitiveness, and promote the industrialization development of terahertz communication technology.
In terms of policy support, the government needs to continue to increase investment and support for terahertz communication technology related topics and projects, and gradually increase demonstration application requirements on the basis of academic research projects, encourage the participation of device manufacturers, equipment manufacturers and operators and other industrial chain roles, lay out project research based on application demand, promote the combination of industry, University, research and application, and promote the industry development. In addition to the technical research related to key devices and systems, it is also necessary to start the research on terahertz communication air port technology, encourage and support the output of relevant technical patents and standards in this direction, so as to make technical reserves for the technical patents and standardized layout of China's 6G communication in the future.
In terms of industry guidance, equipment manufacturers and operators should be encouraged to identify application scenarioses and technical requirements as soon as possible, promote collaborative cooperation between upstream and downstream industries, build a close cooperation and win-win ecosystem, realize continuous breakthroughs and progress of key technologies of terahertz communication, mature technology standardization and industrial chain, and deploy application scenarioses The gradual formation of the case and the application of terahertz communication technology jointly promote the mature development of terahertz communication industry.