Design And Research Of Channel Encoding And Decoding Based On Multi-modal Orbital Angular Momentum In Wireless Communications

With the continuous progress and innovation of communication technology,the lack of spectrum resources had became a bottleneck that was restricting the business expansion in wireless communication.Many technologies that improved the utilization of spectrum resources had been proposed.The vortex electromagnetic waves which were carrying OAM was a new direction for solving spectrum resource problems.The vortex electromagnetic waves had a spiral shape waveform and the modal vortex were orthogonality.It could transmit multi-channel information in the same frequency and at the same time.Because of the multi-modal vortex had mode cross-talk and other issues and reduced system performance.Therefore,it can lead the related channel coding technology into the OAM communication system to improve system performance.By summarizing and analyzing the characteristics of the OAM communication system and then this paper researched the OAM system and channel coding and decoding code deeply.Thus it proposed the method that was leading the channel coding and decoding into OAM communication system.The main works and conclusions are as follows:(1)This paper summarized and analyzed the related concepts and the generating methods of OAM.At the same time we introduced the channel coding and decoding.It built a research basis on the application of that put the channel coding and decoding technology into OAM communication system.At the same time,we summarized the methods of generating OAM and selected a suitable method of generating the vortex to establish the corresponding communication model.This part laid a solid theoretical foundation for the research of this thesis.(2)This paper established the OAM communication system which was based on circular array antenna.The related performance was analyzed and we deduced the capacity of the system.The OAM communication system could be constructed with a circular array antenna that had multiple-elements.It could gotten the different spatial energy distribution to realize different modal vortex by controlling the phase changing between the feed elements.If we assumed that transmit antennas and receiving antennas were coaxial,we could deduced the capacity.The experiment results showed that the capacity of the OAM communication system and the MIMO communication system was the same when the number of the antennas was the same and they had the identical sub-channels.Theoretically the number of sub-channels that MIMO could constructed was limited.But the number of sub-channels that OAM could constructed was infinitely.So it could achieved complex transmission at the same frequency.Therefore,with the number decreasing of OAM sub-channels,the channel capacity of OAM would be larger than MIMO system.At the same time,we analyzed and compared the error rate at the different modulation methods in the OAM system,we could understand the system performance better.(3)This paper proposed to introduce channel coding and decoding into OAM communication system aimed at the problem of system performance degradation caused by cross-talk and divergence in wireless communication.It introduced the classical RS code as a short code scheme into the OAM communication system firstly.After the experiment evaluation of effectiveness was made on channel coding and decoding.It could reduce the bit error probability of the communication system.Considering that the trend of the development of communication was high-capacity.So the LDPC codes as a long code scheme of the coding and decoding was bring into the OAM communication system.After analyzing the three different test matrix construction methods of Gallager,Mackay and QC-LDPC,the optimal coding scheme was selected and then combing with the PEG algorithm which was increasing the circumference and improving the code performance to get the most optimize test matrix.At the same time,the code performance of BP and MS decoding algorithm were comparing,and the appropriate decoding algorithm was chosen as the decoding method for LDPC code.This paper also analyzed the influence of performance of OAM system in different signal-to-noise ratios and code length.At the same time the effect of different code rate and decoding iterations were analyzed for the system.Based on the polar code was put forward in recent years,the model of OAM communication system which was based on polar code was built.It had great research significance in the specific application of OAM in the wireless communication in the future.