KEYWORDS: Telecommunications, Modulation, Wireless communications, Transceivers, Signal generators, Reliability, LabVIEW, Internet of things, Eye, Digital modulation
With the rapid advancement of the Internet of Things, terahertz band has emerged as a prominent area of research for high-speed wireless communication over the past decade to satisfy the growing demand for network traffic and is extensively employed in indoor wireless communication systems. This study experimentally examines the transmission efficacy of MSK signals in terahertz channels via upconversion. In the LabVIEW development environment, the PN sequence serves as the baseband signal. The MSK signal, with a bandwidth of 1GHz and a transmission rate of 1Gbit/s, is modulated and output using the high-speed vector signal transceiver platform, PXIe-5841. This signal is then upconverted to 230~300GHz for wireless transmission. The findings from the constellation and grid diagrams reveal the stable and reliable transmission of the MSK signal in the terahertz communication system, underscoring its viability and potential for future research and application.
Recently, research on 6G wireless communication technology has become a hot topic. In 6G technology, terahertz communication is considered the most promising part. The research and application of the terahertz communication frequency range (0.1-10 THz) will bring revolutionary changes to the field of communication. It has the potential to bridge the transmission gap between the infrared and microwave bands, and offers highspeed data transmission, low latency, and high-capacity communication. Therefore, the development of terahertz communication is highly anticipated as a significant driving force for 6G technology. At present, research on outdoor terahertz channels is far less extensive compared to indoor channels, requiring more efforts to explore the characteristics of outdoor terahertz channels. In this paper, we focus on the three-dimensional scenario of street canyon and model the terahertz channel using ray tracing. The carrier frequencies used for simulation range from 220 to 330 GHz. By calculating the power loss and required time for each path from the transmitter to the receiver, we obtain parameters such as power delay spectrum and power angle spectrum. Next, we analyze the relationships between path loss, delay spread, angle spread, and distance, gaining further understanding of the outdoor terahertz multipath channel characteristics.
6G wireless communication technology is expected to provide a higher peak data rate, lower latency, high mobile speed, high spectral efficiency, and high network energy efficiency in the future. It has the advantages of wide coverage, high security, and low-cost efficiency. As one of the candidate frequency bands of 6G technology, THz wave (0.1-10 THz) bridges the infrared band and the microwave band and has a very important application prospect in the communication process. Due to the terahertz source power and the absorption of various particles in the air, indoor short-range terahertz wireless communication has practical research value. In this paper, for the three-dimensional scene of common indoor conference rooms, the ray tracing method is used to model the terahertz channel of the line-of-sight (LOS) path, the primary reflection path, and the secondary reflection path. The carrier frequency range used for the simulation is 220-330 GHz. By calculating the power loss and required time of each path from the transmitter to the receiver, parameters such as the power delay profile are obtained. Then, the related terahertz channel parameters such as Rician K-factor and root mean square (RMS) delay spread are analyzed.
The vibrational and rotational energy levels of many biomolecules are in the terahertz band, so terahertz technology can be used to detect biomolecules. In addition, because the photon energy of terahertz wave is low and will not destroy biological samples in the detection process, terahertz technology has a very wide application prospect in the future research fields such as biochemical detection and information communication. As we all know, most biomolecules need to be in liquid environment to give full play to their biological activity. However, the hydrogen bond in aqueous solution will produce strong absorption in terahertz band. In addition, water molecules are polar molecules, and terahertz wave has strong resonance absorption to polar molecules, which makes it very difficult to detect active biomolecules in liquid environment by terahertz technology. Therefore, many research teams combine terahertz spectroscopy with microfluidic technology to reduce the impact of various factors on biomolecular detection. In this study, the THz microfluidic chip was prepared with cycloolefin copolymer (COC). The five potassium salt solutions in a constant electric field at different times were studied, which provided a basis for further strengthening the application of THz technology in biochemistry. What’s more, the electrolyte solution contains a large number of anions and cations, which will move under the action of electric field. And it provides technical support for the study of the dynamic characteristics of electrolyte solution by terahertz technology.
Terahertz communication technology has attracted wide attention from academic circles and industry, and is regarded as the key wireless technology to meet the real-time traffic demand of mobile heterogeneous network system, which can alleviate the capacity bottleneck of the current wireless system and realize ultra-high-speed wireless communication. As a key content of Beam-forming Techniques, indoor channel modeling of terahertz band in NLOS (non-line-of-sight) has become an urgent task. In this paper, according to the position of the receiver and the surrounding scenes, the possible path from the transmitter to the receiver is traced back through geometric optics. The influence of diffraction on the transmission channel of 300GHz indoor communication system is evaluated. Ray tracing technology is combined with knife edge diffraction (KED) and double knife edge (DKE) to simulate the diffraction of wedge-shaped object and human body respectively. The results show that when the wedge-shaped object diffracts, the diffraction coefficient decreases with the increase of the diffraction angle. Diffraction in the wedge area can be ignored in most areas of the room's line of sight, but diffraction power is dominant in the incident boundary and reflection boundary area. Due to the shadow effect caused by human movement, the path attenuation increases significantly. The results provide a research basis for the development of indoor terahertz communication.
Terahertz (THz) communication is a research hotspot in the future communication field. However, limited by the power of the THz source and various particles in the air, indoor THz wireless communication with short distance transmission has practical research value. Due to the strong directivity of THz beam, the line of sight (LOS) path occupies most of the energy of the signal. However, when the LOS path is blocked, the not line of sight (NLOS) path can be used as a supplement to ensure the stability of the communication link. In this paper, a 3D transmission model combining LOS path, primary reflection path and secondary reflection path was established by ray tracing method for indoor laboratory scenes with high demand for communication rate. The carrier frequency range is 220-330GHz. Through the results of power delay profile (PDP) and power angle profile (PAP) at the receiver, the correlation characteristics of important channel parameters such as Rician K-factor, root mean square (RMS) delay spread with different frequency points and different paths are analyzed. The results show that all the channel parameters are strongly correlated with frequency and transmission distance. These theoretical results lay a foundation for the subsequent communication experiments in real experimental condition.
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