Research On 5G New Radio Downlink Detection Technology

With the rapid development of wireless communication technology,strict requirements for communication quality such as large bandwidth,high speed,multi-user and low cost have been raised.In order to satisfy the above requirements,the new radio(NR)of the 5th generation communication system(5G)introduces new design in the network architecture,the frame structure and the channel coding,yielding a big difference in the detection of NR signal.Ultra-dense networks(UDN)network architecture,an ultra-dense deployment scheme for cells with limited coverage,is adopted by NR to improve the network capacity.In complex,heterogeneous,and dense scenarios,serious co-channel interference problems are caused by the coexistence of high-density wireless access sites,which lead to the deterioration of spectral efficiency.Therefore,co-channel interference becomes one of the main factors that limits performance of ultra-dense networking technology,bringing a challenge to the detection of co-channel signals.This paper mainly investigates the signal detection problem of the 5G NR downlink system,focusing on cell search,channel estimation and multi-antenna reception under co-channel interference.The main contributions are summarized as follows:First,cell search under co-channel interference is studied.The timing synchronization algorithm and frequency offset estimation algorithm applicable to NR cell search are simulated,in which the adaptability of the algorithm under co-channel interference is analyzed.In order to improve cell search performance with the co-channel,interference cancellation is adopted to improve cell detection performance.The physical cell identification(PCI)of the signal with the strongest power among co-channel cells through cell search is obtained.After the PCI is applied to generate the local secondary synchronization signal(SSS),the least squares estimation based on SSS is carried out to complete the initial channel estimation and obtain the channel response.The cell signal is cancelled from the received signal based on this channel response.Considering the scenario of multiple cells with the co-channel,the signals during multiple interference cancellation combined with SSS channel response are employed for signal reconstruction,which demonstrates that it can effectively suppress error propagation during interference cancellation process.Second,in order to improve the performance of signal detection under co-channel interference,the multi-antenna receiving technology combined with interference rejection combining(IRC)is used to detect the received signals.Aiming at the scenario of multiple cells under co-channel interference,the synchronization signal is used to calculate the channel response to improve the channel estimation accuracy,which can effectively suppress the effect of co-channel interference,and improve the performance of the IRC algorithm.Furthermore,a scheme combining interference cancellation and IRC is proposed to detect cell signals iteratively.The cell signals obtained in the cell search process are sorted by power,and the received signals are detected sequentially by IRC algorithm.The performance gain obtained by the proposed method is used to update the initial channel estimation,more accurate channel response and enhanced performance of signal detection is obtained.