Research On WHT-OFDM Modulation And Demodulation Technology Based On FPGA

Orthogonal frequency-division multiplexing(OFDM)technology has been widely used in broadband wireless communication,with the advantages of high spectrum utilization and resistance to multipath fading.However,in the high-speed scenario,due to the timeselective fading between the subcarriers of the OFDM system,some subcarriers cannot be recovered and the transmission data is lost,resulting in an increase in the bit error rate of the system.In order to improve the performance of the OFDM system,the Walsh-Hadamard transform(WHT)can be combined with OFDM,which can not only improve the bit error rate performance of the OFDM system,but also do not lose the data transmission rate,so WHT-OFDM technology can become an alternative to OFDM.This paper first discusses the transmission characteristics of WHT-OFDM,and then designs and implements WHT-OFDM modulation and demodulator based on FPGA.The specific work of this thesis is as follows:(1)The transmission characteristics of WHT-OFDM communication system are analyzed theoretically.Firstly,a model of WHT-OFDM communication system is established,then the transmission performance of WHT-OFDM and OFDM is compared using Matlab software,and finally the selection of parameters and the design of data frames during the design of WHT-OFDM modem circuit structure is completed with reference to802.11 a protocol.(2)The WHT-OFDM baseband modulator and demodulator was designed.According to the principle of wireless communication system transmitter,the modulator module is decomposed into functional modules such as scrambling code,convolution coding,16-QAM modulation,insertion pilot,WHT operation,IFFT operation,cyclic prefix addition and training sequence generation.The demodulator module is divided into frame synchronization,symbol synchronization,FFT operation,IWHT operation,channel estimation and equalization,pilot removal,16-QAM demodulation,convolution decoding and descrambling code.According to the principle and design scheme of each functional module,the circuit design is completed in Verilog language,and the correctness of the design of each functional module is verified by Vivado software simulation.(3)Simulation verification of the integrated WHT-OFDM modulator and demodulator.First,binary data is generated using Matlab as the input data for the modulator.Then,the data output by the modulator after modulation is superimposed with noise generated by Matlab,which serves as the input data for the demodulation module,and the demodulation simulation is completed.Finally,the recovered data from the demodulation is compared and analyzed with the binary data generated by Matlab to verify the correctness of the designed WHT-OFDM modulator and demodulator.