Research On Adaptive Coding And Modulation For Data Link Of Shipboard Unmanned Aerial Vehicle

As the main means of detection and early warning of marine information,shipboard unmanned aerial vehicle send the marine information to the base station through data link.With the application of a new type of sensor in unmanned aerial vehicle(UAV)data link,the data need to return are growing exponentially.At present,UAVs use a single data link structure,in which case the return rate is slow and can not meet the rapid and efficient data return requirements,this is a major problem affecting the development of UAVs.In order to solve this problem,upgrading and reforming the structure of the data link is an effective means,as the coding and modulation is important module in the UAV data link,so it has important significance to study it.Now UAV choose the transmission scheme based on the worst channel in order to ensure the normal communication when working at sea.This method can ensure the normal communication even when UAV work in the worst channel,however,it leads a great waste of system throughput when UAV work in good channel.In this paper,in order to maximize the channel capacity,improve the throughout,shorten the transmission time,and reduce the possibility of UAVs discovery,adaptive coded modulation techniques are introduced.LDPC code is a good code with low coding complexity,strong error correction ability and high coding gain performance,and the code structure is rich,which can realize simplified coding and parallel decoding.The application of LDPC codes and adaptive coded modulation techniques to data link can improve the throughout of the feedback information while ensuring the reliability of the system.Therefore,it is important to study the adaptive coded modulation technique of UAV data link based on LDPC codes.The purpose of this paper is to establish a set of adaptive coded modulation transmission scheme based on the maritime channel,which combines the LDPC code,the high order modulation technique and the channel estimation technique,to improve the throughput of the UAV.The main contents of this paper are as follows:(1)The propagation characteristics of electromagnetic wave in Shipborne UAV communication are researched.Then analyze the factors causing the fading,at last,determine the mathematical model of UAV-warship channel.(2)Simulate the performance of RS code,convolutional code,Turbo code and LDPC code and analyze their ability of disturbance.Deduct the decoding initialization process under the case of high order modulation and Nakagami fading channel.(3)Deduct the SNR estimation formula and evaluate their performance under the channel of Nakagami,which provides theoretical support for adaptive coded modulation technology used in maritime channel.Then a weighted SNR estimation algorithm for channel estimation of 16 APSK signals is proposed.(4)Determine transmission mode.Analyze and simulate the performance of each coded modulation scheme in the Nakagami channel,and then determine the transmission scheme of the adaptive coded modulation system.(5)Study on adaptive switching algorithm and evaluate the adaptive transmission scheme.Adaptive switching algorithms are studied,and then we compared their performance.Finally,the performance of the adaptive modulation mechanism is compared with the fixed coding modulation.