Design And FPGA Implementation Of Fading Channel Simulator For Wireless Communication

With the rapid development of wireless communication technology,the design and development of communication devices become more and more complex,and the demand for wireless communication testing is increasing.Since wireless electromagnetic wave signals are subject to energy fading and electromagnetic wave scattering,the performance of wireless channels is exceptionally complex,making system verification testing of wireless communications more difficult.In the actual development process,multiple field tests in real wireless environments are required,but doing so will consume a lot of manpower and resources.Therefore,the wireless fading channel simulator has important research value,it can provide a variety of repeatable channel environments,improve test efficiency and shorten the development cycle.Thesis expounds the theoretical basis of wireless channels,including additive Gaussian white noise channel,large-scale fading channel and small-scale fading channel.Three key technologies of the wireless fading channel simulator are studied and simulated.Firstly,a method based on the remainder system is investigated for generating Gaussian white noise sequences.The core of this method is to select the appropriate permutation polynomial and use the Chinese remainder theorem for mapping.In this way,the iterative operation with a very large bit width can be divided into multiple operations on small dynamic ranges,so as to reduce the bit width of the iterative loop in hardware implementation.This method can generate long-period random sequences obeying Gaussian distribution at high speed.Secondly,the high-precision delay technology is researched and simulated.Four design methods of fractional delay filters are analyzed,including the direct truncation method,the method of adding window functions,the Lagrangian interpolation method and the design method based on the Farrow structure.The Lagrangian fractional delay filter based on the Farrow structure has good amplitude-frequency characteristics and group delay characteristics,and can achieve variable fractional delay without updating filter coefficients.Then,the wireless fading channel model is studied and simulated,and two classic channel models are introduced: Clarke model and Jakes model.The Clarke model performs well,but is physically unrealizable.The Jakes model has a simple structure,but poor performance.The improvement of the Jakes model by related scholars in the existing literature is analyzed in detail.The improved model not only has excellent statistical properties,but also can be implemented with less hardware resources.Finally,the hardware implementation structure of the wireless fading channel simulator is proposed,and the design of three key modules is described in detail: the Gaussian white noise module based on the remainder system,and the high-precision delay module based on fractional delay filter of the Farrow structure and the Rayleigh fading module based on Jakes improved model.The system testing and result analysis of the wireless fading channel simulator are carried out,including testing and analysis of statistical characteristics and bit error ratio,which verifies the correctness of the wireless fading channel simulator.