Study On Multi-Carrier Transmission Performance Based On Polar Codes In Vehicle Channels

With the improvement of people’s quality of life,the number of cars is also gradually increasing,and road traffic safety and traffic efficiency have gradually attracted people’s attention.The Internet of Vehicles technology can transmit information between vehicles in the form of wireless communication to ensure road safety and improve transportation efficiency.In order to ensure that the traffic warning information and traffic congestion information can be transmitted in a timely and accurate manner when the vehicle is running,higher requirements are placed on the communication quality of the Internet of Vehicles technology.The high-speed moving characteristics of vehicles,the time-varying inter-vehicle distance,and the complex wireless propagation environment seriously affect the communication quality of the Internet of Vehicles.Therefore,it is of great significance to study the channel coding technology in the digital communication system to improve the communication quality of the vehicle network.As the latest encoding and decoding scheme in 5G communication,Polar code is the only encoding method that can theoretically reach the Shannon limit.However,there are still some deficiencies in practical application scenarios.In practical applications,the code length is usually limited.At this time,due to insufficient channel polarization,the performance of Polar codes is not ideal.Although some scholars have proposed some high-performance decoding algorithms for short codes length,the actual communication efficiency is affected by the high complexity and decoding delay of high-performance decoders.In response to these problems,this paper mainly does the following work:First,this thesis studies and analyzes the SCL and SCS decoding algorithms.As the breadth-first and depth-first code tree search decoding algorithms,they can achieve better decoding performance than the SC algorithm.In view of the high complexity of the SCS decoder,this paper divides the code block into multiple sub-blocks according to the error probability of the sub-channel,and then places the parity check at the position of the burst error,so that the SCS decoder can detect the wrong decoding path and deleted in time,and path splitting and path sorting are only performed on subchannels with low reliability,which reduces the complexity and complexity of the SCS decoding algorithm without losing the decoding performance.Second,this thesis analyzes the performance and complexity of the list decoding algorithm and sequence decoding algorithm of PAC codes,and then applies the strategy of reducing the number of path splits with reference to Polar codes to reduce the complexity of list decoding.And prove that when path splitting and path screening are performed at the information bit positions,if all the paths extended from the original path are deleted,then the decoding path with the smallest path metric in the original path is the ML decoding path.Path pruning is performed to reduce the average list size for list decoding.Finally,in the vehicle channel environment,a multi-carrier transmission system based on Polar/PAC code is built.First,the performance of Polar code and PAC code is compared,and it is proved that PAC code has the better performance as polar code in vehicle channel under the same decoding complexity.The proposed low-complexity decoding algorithm of Polar/PAC codes is simulated and tested in the vehicle channel.The experiment proves that when the vehicle travels at a high speed and the channel environment is poor,the low-complexity decoding algorithm is extremely effective for high bit rate.There will be a certain performance loss in the decoding of the Polar/PAC code.