Research On Signal Processing Method Of Terahertz Communication Based On CPM

The increase of wireless transmission rate has promoted the development of new applications and changed people's daily life.In turn,new application scenarios have also put forward higher requirements for communication systems.With the fifth generation mobile networks(5G)gradually moving towards the commercial stage,various countries have begun research work on higher frequency band Terahertz(THz).Terahertz communication can support higher communication rates,and has high security and strong anti-interference ability.It is considered to be one of the key technologies for next generation mobile communications.Because the terahertz wave attenuates greatly in the air,the transmission distance of terahertz communication is limited.Combining terahertz communication with Continuous Phase Modulation(CPM)technology with high power efficiency can effectively improve this problem.Therefore,it is of great significance to study terahertz communication based on CPM.In order to apply CPM to terahertz communication,this paper focuses on the frequency domain equalization and phase noise compensation in the single-carrier CPM systems.The main research work can be divided into two parts:Research on frequency domain equalization of CPM system: firstly,two problems arise when CPM is combined with frequency domain equalization technology.The frame structure that can maintain phase continuity and the principles of two discrete linear decomposition are described.Secondly,the traditional frequency domain equalization methods of CPM under two kinds of decomposition are analyzed respectively.It is concluded that the frequency domain equalization complexity of CPM is mainly determined by the number of parallel equalization paths.Because the orthogonal representation of CPM generated by three inner products is different,a frequency domain equalization method based on approximate orthogonal decomposition is proposed by selecting the best combination of approximate orthogonal basis.Finally,the simulation results show that compared with the traditional frequency domain equalization method based on orthogonal decomposition,the proposed method can effectively ensure the performance of frequency domain equalization while reducing the complexity.Research on phase noise compensation of the CPM system: firstly,the impact of three non-ideal front ends on the system is analyzed,and the influence of low-precision quantization and phase noise on the three modulation methods is simulated and compared.Then,the principle and flow chart of phase noise compensation based on CPM are given by means of frequency equalization based on orthogonal decomposition.Secondly,based on the idea of Common Phase Error(CPE)averaging and linear interpolation and decision-feedback iterative Least Mean Square(LMS),two non-iterative compensation methods and one iterative compensation method applied to CPM systems are respectively studied.Then,a low complexity iterative LMS compensation method is proposed by improving the structure of CPM demodulation and re-modulation in the iterative process.Finally,the simulation results show that the phase noise compensation methods can effectively compensate the influence of phase noise on CPM systems under frequency selective channel,and the performance of the proposed low-complexity iterative compensation method is close to the original iterative LMS compensation method.