Research And Implementation Of FQPSK Soft Demodulation And LDPC Decoding Algorithm

UAV(Unmanned aerial vehicle)is an emerging method of beyond-horizon communication.In recent years,because of its flexibility,it has been widely used in various fields such as aerial photography,agricultural plant protection,power inspection,public safety,and logistics.On the one hand,the complex and changeable wireless channel environment,resulting in inter-symbol interference problems restricts the development of UAV systems.On the other hand,the limited size of the UAV makes the UAV system have higher requirements for spectrum utilization and power efficiency.In this paper,single carrier frequency domain equalization(Single carrier frequency domain equalization,SC-FDE)technology is used to eliminate inter-symbol interference,reduce the impact of frequency offset and synchronization error,and at the same time obtain a lower peak-to-average ratio.Considering that the SC-FDE system tends to adopt a low-cost non-linear power amplifier,this paper uses a non-linear modulation scheme with high spectral efficiency and power efficiency-FQPSK modulation.In order to solve the problem that the FQPSK waveform is susceptible to noise interference,this paper uses the powerful error correction capability of the LDPC code to make up for the defects of the FQPSK modulation scheme.This paper combines the advantages of LDPC codes and FQPSK modulation to provide a feasible solution for UAV systems with low peak-to-average ratio,high spectrum utilization and high power efficiency.This paper focuses on the design of the transmitter and receiver in the UAV communication system,respectively studied the modulation and demodulation of FQPSK,and the coding and decoding of LDPC.