5G MIMO Channel Emulation Method And Application With Variable Bandwidth And High Precision Delay

The wireless channel simulator simulates the path loss,multipath,fading and other related characteristics of the transmitted signal from the antenna port through the wireless environment in real time,and accurately simulates the impact of the wireless environment on the performance of the communication link system in the laboratory,and verifies the system equipment and the performance of the terminal in various complex scenarios.The high bandwidth and Massive MIMO(Multiple Input Multiple Output)technology in5 G mobile communications put forward higher requirements for the channel delay accuracy in analog technology.Variable Fractional Delay(VFD,Variable Fractional Delay)technology is widely used in sampling rate conversion,filter design,array signal processing and voice processing due to its flexible and variable delay value.This technology is usually implemented using an all-pass filter design,and the more classic filter structure is called the Farrow structure.Once the Farrow filter structure is selected,the design of its filter coefficients becomes a core issue.This paper is based on an improved method of generating sub-filter coefficients of Farrow filter structure,which realizes that the two parameters of cut-off frequency and group delay can be flexibly adjusted at the same time.According to the required simulation channel parameters and accuracy,the required sub-filter coefficients are calculated,thereby realizing the efficient design of the variable fractional delay filter.The designed variable bandwidth fractional delay filter has a wide range of adjustable bandwidth and precise fractional delay function.When the filter coefficients do not need to be updated,the group delay and bandwidth of the filter can be adjusted by adjusting the delay or bandwidth configuration parameters.Each transmitting and receiving channel only needs to use one filter to realize the simulation of different bandwidth wireless channels,which improves the simulation accuracy.In the application of massive MIMO channel simulator,this method saves channel coefficient storage space and reduces system resource consumption.This paper analyzes the complexity and performance of the variable bandwidth fractional delay filter.The coefficients of the Farrow structure subfilter of the variable bandwidth fractional delay filter under different delays and cut-off frequencies are calculated.Simulation analysis is performed.Its amplitude-frequency and phase characteristics are integrated into the channel simulator algorithm processing module for complete simulation verification.Finally,module-level and system-level verification tests were performed on the hardware platform,and a complete test process of channel simulation between 5G base station signals and wireless terminals was realized,and the verification results were in line with expectations.