Research On Reliable Transmission Of Train-to-Ground Safety-related Data Based On Polar Codes

As a newly-developing channel coding,Polar code has been proved to approach Shannon limit theoretically with low complexity of coding and decoding.Hence,Polar code,once published,has become an attractive topic for domestic and foreign scholars.In order to provide a more reliable wireless transmission link for the train control system,Polar code can be applied to the reliable transmission of mission-critical data of the next generation of railway train-to-ground wireless communication system because of the excellent performance.The main researches of paper are organized as follows.(1)We propose a construction scheme of Polar code to transmit the mixture of data with different reliability requirements,which based on the channel polarization.And this scheme will be applied to the train-to-ground wireless communication scenario to improve the transmission reliability of safety-related data.In order to select the channels to transmit safety-related data and safety-unrelated date,we design two selection schemes to further improve the reliability of the safety-related data based on the criteria of channel reliability metric.Simulation results show that the second channel selection scheme has better performance,it can select better channels for the safety-related data so as to improve the transmission reliability.(2)We analyze the SC decoding algorithm and SCL decoding algorithm,and proposed the SCL-SC decoding algorithm to further improve the transmission reliability of mission-critical data based on the construction scheme which transmits the mixture of safety-related data and safety-unrelated data.This algorithm also based on the second channel selection scheme.The performance of SCL-SC decoding algorithm is compared from four aspects of SCL decoding ratio,search width,bit rate and safety-related data ratio in this paper.(3)In the actual scene of train-to-ground communication,channel state information(CSI)can affect the performance of communication system significantly.Because of the high-speed relative motion,rapid variation of channel makes it difficult to obtain the real-time CSI,and the decoding at receiving terminal will be affected by undesirable CSI.In this thesis,we design an enhanced Wireless Communication Transmission Protocol.On the basis of historical CSI,so that the receiver and the transmitter can obtain more accurate CSI with the protocol.In addition that,this protocol can coordinate the polar codec parameter of the receiver and the transmitter.