Research On Non-Orthogonal Coded Access Technology Based On 5G Application Scenarios

The fifth generation mobile communication technology(5G)has become a research hotspot at home and abroad,and the research on 5G new radio(NR)is becoming increasingly refined.As one of the key technologies of 5G NR,Non-Orthogonal Multiple Access(NOMA)technology achieves multiple users access by superimposing multiple users on the same time-frequency resources,which can support the individualized requirements of different application scenarios.At present,the industry has initially verified that NOMA scheme brings obvious gains in system throughput and user connection,but its performance in the actual application scenario remains to be further studied.Non-Orthogonal Coded Access(NOCA)is a 5G candidate multiple access scheme.Each user applies different spreading sequences,and each data symbol is spread and then mapped to multiple subcarriers to enhance anti-interference ability.At the same time,combined with grant-free transmission mechanism,NOCA can simplify signaling to reduce transmission latency and reduce power consumption of terminal equipment.In this paper,NOCA technology is focused,link performance studies in 5G application scenarios are conducted as well as two different aspects,including uplink Peak to Average Power Ratio(PAPR)suppression and uplink user detection,are analyzed.The main work and innovations are as follows:Firstly,the design of uplink grant-free based NOCA system is optimized,and the performance of NOCA is evaluated.Based on the analysis of NOCA system mechanism,this paper designs a low cross-correlation spreading sequence pool extraction scheme according to various spreading factor(SF),which optimizes the construction of NOCA spreading sequence pool.Then,two types of uplink physical resource allocation schemes are analyzed,and link level simulations of various SF are carried out combined with the 5G application scenarios.In mMTC and eMBB application scenarios,the block error rate of various SF and corresponding SF adaptation schemes are obtained,which provide a reference for the standardization of 5G multiple access technology.Secondly,PAPR exacerbation in NOCA is studied.In this paper,the mathematical expression of PAPR for single-carrier and spread-spectrum system are theoretically erived,and a PAPR suppression scheme is proposed based on the analysis of the PAPR exacerbation in NOCA.Compared with traditional PAPR suppression schemes,the proposed scheme can effectively suppress the excessive PAPR in NOCA system,which makes it comparable to CP-OFDM.It also provides obvious gains on the block error rate performance.In addition,the proposed scheme has advantages of strong feasibility and low hardware design cost,and it is suitable for uplink transmitter design of NOCA system.Thirdly,uplink user detection for NOCA is studied.This paper designs an uplink user detection system for NOCA based on the Neyman-Pearson criterion,and studies the miss detection rate performance with different time-frequency resource allocation schemes for the detection sequence.The simulation results show that the frequency selectivity of the fading channel has significant impacts on the user detection performance.In order to achieve low latency and ultra reliability in URLLC scenario,it is necessary to comprehensively consider the factors such as channel characteristics,time-frequency resource allocation,data validity and so on to design the user detection system.