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.
KEYWORDS: Telecommunications, Denoising, Oscillators, Signal to noise ratio, Interference (communication), Information and communication technologies, Terahertz radiation, Signal generators, Transmitters, Antennas
With the rapid development of 5G communication technology, terahertz wave has attracted extensive attention due to its large capacity, good directivity and strong anti-interference ability. However, in the terahertz communication system based on the subharmonic mixing method, in the process of generating the terahertz signal, due to the high frequency multiplication, the floor and phase noise of the original frequency source pass through the frequency doubling and amplification links, and the spectrum is realized. The shifting and amplification are degraded, while the circuitry of the link itself also produces an in-band noise superposition. In order to reduce noise, this paper studied on the basis of the principle of harmonic mixing terahertz communication system of the high harmonics and the vibration noise impact on the quality of communication, this paper proposes a method of harmonic interference suppression method this method by selecting the required harmonic band-pass filtering, set the appropriate frequency range can make other harmonic component to fall outside the frequency band, so as to achieve effect of reducing the noise of a terahertz communication system.
KEYWORDS: Signal to noise ratio, Telecommunications, Wireless communications, Information and communication technologies, Modulation, Interference (communication), Terahertz technology, Demodulation
With the advent of the 5G era, the demand for wireless communication rates is increasing, making high-speed wireless communication become a hot spot and focus. Due to the wider frequency bandwidth and good confidentiality, the terahertz band has attracted wide attention in the field of high-speed wireless communication above Gbps. However, terahertz wave is easily absorbed by water and attenuates seriously when it is transmitted in the atmosphere, which seriously restricts the development of communication in the terahertz band. However, the spread spectrum communication has attracted much attention in the field of terahertz communication because of its strong anti-fading, anti-interference and good confidentiality. In this paper, the simulation model of direct sequence spread spectrum (DSSS) communication system is established by using MATLAB, and the baseband signal and m-sequence spreading code of different rates are set, and 310GHz is used as the carrier frequency to transmit in additive white Gaussian noise channels with signal-to-noise ratio (SNR) of 17dB to -1dB. Medium transmission, by checking the bit error rate (BER), to verify the anti-interference of the DSSS technology applied in the terahertz band. The simulation results show that when the spread spectrum gain is large, the DSSS can be used in terahertz communication under the same BER to transmit in channels with a SNR of 10dB worse. Therefore, the application of spread spectrum communication technology to terahertz communication has a good development scenario and will effectively promote the development of terahertz communication.
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