Co-time Co-frequency Digital Interference Suppression Algorithm Between 5G Stations And Experimental Verification

To improve the spectrum resource efficiency,the 5th Generation Mobile Communication Technology adopts the dynamic time division duplex technology based on flexible time and frequency resource allocation.However,the different subframe ratios between neighboring base stations will cause co-time co-frequency interference between inter-station crossover subframes,which can affect the reception of the desired signal correctly when the deployment distance between neighboring base stations cannot meet the isolation requirement.Therefore,it is necessary to study inter-station co-time cofrequency interference suppression techniques to guarantee the correct demodulation of the desired signal.In this thesis,we focus on 5G inter-station co-time co-frequency interference suppression technology,design the structure of 5G inter-station co-time cofrequency digital interference suppression system,propose the inter-station interference frequency domain suppression algorithm,and complete the simulation and FPGA implementation verification of interference suppression.The details of the study are as follows.Firstly,the time synchronization and frequency synchronization strategies under the inter-station interference suppression system are designed.The overall structure of the 5G inter-station interference suppression system is designed for the co-time co-frequency interference caused by inter-station crossover subframes.Based on this system,a timefrequency synchronization strategy is proposed,and the theoretical derivation and simulation analysis of the time synchronization algorithm and frequency offset estimation algorithm are completed.The simulation results show that the detection probability of the time-synchronization algorithm reaches above when the interference-noise-ratio is-6d B,and the normalized root mean square error(NRMSE)of the frequency offset estimation is close to 0.1 when the interference-noise-ratio is 20 d B in the mixed Gaussian and Rayleigh channels.Secondly,the inter-station co-time co-frequency interference frequency domain suppression algorithm is designed.Based on the 5G inter-station interference suppression system,the inter-station interference frequency domain suppression algorithm is designed,the influencing factors of the inter-station interference frequency domain suppression performance are analyzed,the simulation structure of the inter-station interference frequency domain suppression algorithm is established,and the effects of time synchronization error and frequency synchronization error on the inter-station interference suppression performance are simulated and analyzed.The simulation results show that when the interference-noise-ratio is 20 d B,if the time synchronization error is less than 10 code pieces,the interference suppression performance deteriorates less than0.5d B,and if the frequency synchronization error is between-800 Hz and 800 Hz,the interference suppression performance loss is within 3d B.Finally,the inter-station co-time co-frequency digital interference suppression implementation and verification are completed.The overall implementation structure of the inter-station interference suppression system is designed,the detailed logic and workflow design of the frequency-domain interference suppression algorithm based on FPGA is carried out,and the experimental verification platform of the inter-station interference suppression system is built,and the frequency-domain interference suppression performance test is completed.The results show that the interference signal passing through the RF channel will introduce nonlinearity,thermal noise,resulting in a loss of about 3 d B in the frequency domain interference suppression performance test results compared to the simulation results.The frequency-domain interference suppression algorithm and time-frequency synchronization strategies studied in this thesis are successfully applied to the co-time cofrequency digital interference suppression system between 5G stations,which provides a theoretical basis and engineering implementation reference for further research and exploration of dynamic time-division duplex communication systems.