Research On OTSM Modulation And Demodulation Technology And Its FPGA Implementation

Orthogonal time sequency multiplexing(OTSM)is a single carrier modulation technique suitable for high mobility scenes.Its principle is to multiplex information symbols in delay and sequency domain by using time division multiplexing and Walsh-Hadamard multiplexing cascade.Because the OTSM system uses Walsh Hadamard Transform(WHT)to encode the baseband signal,it only needs simple addition and subtraction operations,so the complexity is low,which is beneficial to hardware implementation.According to the principle of OTSM modulation and demodulation technology,this thesis designs and implements an OTSM modulator and demodulator based on FPGA.The main research contents are as follows:(1)The performance of OTSM modulation technology in high mobility communication scenarios is modeled and analyzed.According to the modulation principle of OTSM,an OTSM system based on Extended Vehicular A(EVA)channel model is built on MATLAB software,and the error performance of OTSM system at different relative moving speeds is simulated,and the error performance of OTSM,OFDM and OTFS systems under Rayleigh fading is compared at the same moving speed.The results show that high Doppler frequency shift can improve the bit error performance of OTSM system,which is superior to OFDM technology applied in 5G system.(2)Design the key functional modules of OTSM modulator and demodulator.The key modules of modulator and demodulator are designed by Verilog hardware description language,and the correctness of the design is verified by Model Sim software and MATLAB software simulation.The designed functional modules include IFWHT module and FWHT module,QAM mapping module and inverse mapping module,row column transformation and adding cyclic prefix module.For the problem that traditional FPGA algorithm can only realize one-dimensional fast Walsh-Hadamard transform with a fixed number of points,a parameterized design scheme is proposed,so that the designed FWHT/IFWHT module can modify the data bit width and the number of transform points.(3)Design,adaptation and verification of parameterized OTSM modulator and demodulator based on FPGA.According to the actual design requirements,the bit width of baseband data can be set in the top module of the system,and the data processing capacity,the operation points of FWHT and the data processing process of each module can be controlled to realize the flexible configuration of the system.Finally,the design software is used to verify the modulator and demodulator,and the results show that the design meets the expected requirements.