Research And Implementation Of High Coding Gain LDPC Decoding Technology For Wireless Optimal Communication

Wireless optical communication is a hotspot in domestic and foreign research in large capacity and secure communication field.In the near-field wireless optical communication link,due to the existence of atmospheric turbulence effect,caused the random transmission of optical signals and the presence of inter-symbol interference between the optical signal and other phenomena,affected the communication performance.Channel anti-jamming coding technology,can effectively alleviate or inhibit the above-mentioned effects in a certain extent,is an important research content in the field of wireless optical communication.The LDPC code is a "good" code with a performance close to the Shannon limit.The LDPC code is applied to a wireless optical communication system,which can brin g high coding gain to the wireless optical communication system and improve the performance of the wireless optical communication system.In this thesis,the analysis of atmospheric turbulence characteristics is carried out,and the influence of turbulence channel on the performance of wireless optical communication is analyzed.The basic theory of LDPC code is analyzed.On this basis,the high coding gain LDPC decoding technology of wireless optical communication is studied and implementation.Based on the LDPC code of IEEE802.16 e standard,this thesis analyzes the coding algorithm based on Gaussian elimination,the approximate triangular matrix coding algorithm and the fast coding algorithm,and completes the scheme design of the encoder and the circuit realization based on Xlinx XC7 A series chip.The hardware platform based on Xlinx XC7 A series chip is built and the simulation is verified to verify the correctness of the algorithm.Based on the analysis and comparison of common decoding algorithms for LDPC codes,the normalized min-sum decoding algorithm algorithms are used as LDPC code decoding schemes,taking into account the coding gain and hardware implementation complexity of the soft decision decoding algorithm.This thesis completes the design of the basic structure of the decoder,and uses the simulation analysis and verification method to further determine the normalized calibration factor of the normalized min-sum decoding algorithm and the number of decoding iterations.This thesis completed the design of the minimization and decoder circuit,and completed the realization and simulation of the decoder circuit based on Xinlinx XC7 A series chip.The simulation results showed that the design of the decoder is correct.Based on the hardware platform of Xinlinx XC7 A series chip,this thesis presents the board level test and verification.Set up the turbulence channel wireless optical communication link performance test platform to carry out system level test verification.The test results show that the coding gain of the LDPC code with code length of 2304 and bit rate of 5/6 is 5.07 dB under the test conditions.The results show that the proposed algorithm is feasible and effective.