Research On Short Frame Communication And Pilot Signal Mapping Patterns Based On LTE System

Ultra-Reliable Low latency Communications is a typical application scenario of the fifth-generation mobile communication system,the air interface delay requirement of u RLLC for data transmission is controlled within 1 ms.Because the air interface delay of the existing Long Term Evolution(LTE)system is about 10 ms,the delay requirement of the millisecond level in this scenario cannot be met,it is meaningful to study how to carry out the evolution on the existing Long Term Evolution system to meet the delay requirements of the scenario.It is considered to be a feasible low-latency technical solution to reduce the communication delay by shortening the length of LTE sub-frame.In this paper,5G low-latency preview using short frame technology is studied,based on the existing LTE system,the downlink short frame design is carried out,aiming at the pilot pattern of short frame,this paper studies and analyses its influence on system throughput and bit error rate,and proposes an adaptive pilot mapping algorithm for short frame in the Internet of Vehicles scenario.Firstly,after discussing the downlink physical layer structure and the timefrequency resource distribution of LTE system,this paper analyses the components of the downlink communication delay,and introduces three feasible methods to reduce the delay.The transmission characteristics of wireless channel are also studied.The channel fading characteristics,such as Doppler frequency shift and time delay expansion,are discussed.The channel modeling of LTE system is introduced.The main problems faced by wireless channel in high-speed mobile environment of vehicle network are pointed out.Secondly,based on the downlink of LTE system,the length of sub-frame is reduced by reducing the number of symbols of Orthogonal Frequency Division Multiplexing in each sub-frame while keeping the subcarrier spacing unchanged.Aiming at the shortcomings of the existing short frame technology,in order to balance the relationship between system throughput and channel estimation quality,we present a cell-specific reference signal mapping pattern based on slot-level short frames and each sub-frame as the basic unit of pilot mapping.The simulation results show that the newly designed short frame pilot pattern can reduce the bit error rate of the system and improve the reliability of communication while meeting the downlink throughput requirements of the LTE system.Finally,the above-mentioned slot-level short frame with new pilot pattern is applied to the vehicle network communication to meet the delay requirement in the vehicle networking communication.Due to the rapid change of the moving speed of the device terminal in the vehicle networking environment,aiming at the problem of the configuration of pilot signals in short frames,an adaptive algorithm for mapping reference signals with different periods according to the current road grade and road congestion is proposed,that is,according to the difference of the road grade of the vehicle and whether or not traffic jam occurs during the current driving,different periods are selected for intra reference mapping.The simulation results show that this scheme can improve the throughput of the system and the utilization efficiency of spectrum resources under the premise of guaranteeing a certain bit error rate for different vehicle driving environments.