Research On Terahertz Integrated Sensing And Communication Technology Based On OFDM

With the advent of the 6th generation mobile networks(6G),some emerging technologies not only require high-quality wireless communication capabilities,but also require stable and high-precision sensing capabilities.Communication and sensing are two of the most common and important applications of traditional radio technologies.Generally speaking,they have different functions and frequency bands.Sensing is mainly used for long-range target detection and identification,while communication is responsible for the transmission of information and data,so they are designed independently.With the advent of 6G,the wireless communication frequency band will gradually transition to the terahertz frequency band,making the two have crossed in the frequency domain.Therefore,the research on terahertz-based integrated sensing and communication technology is of great significance.As one of the most widely used technologies in existing communication systems,orthogonal frequency division multiplexing(OFDM)can realize the rapid evolution of equipment by studying its capabilities in communication-aware integration.At the same time,the application of the traditional OFDM integrated sensing and communication scheme in the terahertz frequency band will also bring some new challenges.According to this main line,thesis mainly does the following research:1)First,thesis reviews and summarizes the propagation characteristics of terahertz waves,and establishes a channel model for terahertz communication and perception.Then,OFDM technology and principles are studied,including the principle of orthogonality,system digital implementation method,communication demodulation process,and the role of guard interval and cyclic prefix.Then,thesis introduces the definition of radar ambiguity function,analyzes the radar ambiguity function of OFDM signal,studies the sensing principle of OFDM,and introduces its characteristics of perception.2)When considering the terahertz frequency band and high-speed mobile scenarios,the traditional OFDM integrated sensing and communication scheme will produce a large Doppler frequency deviation.Then,the impact of Doppler frequency offset on communication and sensing was analyzed,and the scheme of adding pilots at the sending end,the discrete Fourier transform algorithm with the non-origin as the starting point,and the joint algorithm for coarse and fine estimation of speed were proposed,and finally achieved the goal of maintaining The speed detection range is greatly expanded under the condition of the original speed resolution.3)In order to improve the distance resolution without reducing the maximum unambiguous distance,thesis proposes a dual-sub-band OFDM waveform concept,in which the sub-carrier spacing in different sub-bands is independent of each other,but this waveform has interference between sub-bands.For this reason,thesis analyzes the cause of inter-sub-band interference and eliminates it.And integrated sensing and communication system based on dual sub-band OFDM without inter-sub-band interference is realized.Based on this system,a joint sensing algorithm for distance is proposed,which achieves the maximum unambiguous range extension and maintains a good distance resolution ability.