Research On Full Duplex Technology Based On 5G NR

The 3rd Generation Partnership Project has developed 5G(The 5th Generation Mobile Networks)NR(New Radio)technical standards.The technology of 5G has the characteristics of high speed,low latency and large connection.With the increase of the number of UE(User Equipment)in life,the existing commercial deployment of 5G will not meet the needs of users.Full duplex technology can effectively improve system utilization and achieve flexible resource configuration.Therefore,it is of great significance to study the full duplex technology that can be applied to the existing 5G communication system.We first study the reference signal design of co-frequency co-time full duplex system.The technical difficulty in full duplex is SI(SelfInterference)cancellation.SI channel estimation and reference signal design are closely related to SI cancellation.The correlation between the reference signals of uplink and downlink is analyzed in this thesis.In the case of high correlation between the reference signals,the position overlap between the downlink SI reference signal and the uplink data signal can be considered to achieve lower correlation and improve the SI cancellation effect.Under the linear system assumption,both theoretical analysis and simulation results show that the lower the correlation between the SI reference signal and the uplink signal,the more accurate SI channel estimation,the smaller the residual SI,and the better the demodulation performance of the uplink signal.The nonlinear factors cannot be ignored in full duplex mode.The simulation results show that with the increase of SI power,the nonlinear interference results in the system performance loss.In full duplex,downlink SI and uplink signal asynchrony will result in system performance loss.Theoretical analysis and simulation results show that SI arriving in advance seriously reduces system performance,and frequency offset compensation is needed to ensure SI cancellation effect.Compared with the reference signal design of NR,the reference signal design scheme proposed has little change,is convenient to implement,and can achieve better SI cancellation effect.Then,we study and evaluate the sub-band full duplex interference suppression scheme.It is assumed that all cells adopt the same sub-band configuration,gNB(the next Generation Node B)adopts full duplex mode,and UE adopts half duplex mode.Based on the link budget and interference calculation model,a variety of interference quantities in the sub-band full duplex are calculated,including SI of gNB,CLI(Cross-Link Interference)of inter-gNBs and CLI of inter-UEs.Theoretical analysis shows that SI of gNB is much larger than others,which seriously affects the signal receiving of gNB.When the channel condition is good and UE is not far from gNB,CLI of inter-gNBs is very little.When the distance between UEs is very close,CLI of inter-UEs seriously affects the signal receiving of UE.The suppression schemes based on band isolation and enhanced IRC(Interference Rejection Combining)receiver are proposed for SI of gNB,CLI of inter-gNBs and CLI of inter-UEs.The simulation results show that the proposed enhancement schemes suppress the interference in the subband full duplex to some extent.In conclusion,compared with the existing reference signal design,the reference signal design scheme of co-frequency co-time full duplex system proposed in this thesis has little change,which can achieve the purpose of reducing overhead,and SI cancellation effect is better.For the interference existing in the sub-band full duplex,the schemes of using frequency band isolation and enhanced IRC receiver are easy to operate,which can suppress interference and improve the system performance.It provides a reference for the configuration and practical application of the sub-band full duplex system.