Research On NB-IoT Downlink Receiver Connection Technology

With the application of 5G technology,the concept of the Internet of Everything is about to emerge.3GPP(3rd Generation Partnership Project)first proposed the Narrowband Internet of Things(NB-IoT)technology in 2016.Since its introduction,the global communications industry has carried out in-depth research on NB-IoT technology.NB-IoT technology and algorithm iteration,3GPP has completed the freezing of the R16 version of the protocol in June 2020,and NB-IoT technology has become more mature and complete.As an emerging Internet of Things communication technology,NB-IoT has great development potential in the 5G communication era by virtue of its advantages of low power consumption,wide coverage,low cost,and massive connections.In actual application scenarios,NB-IoT devices need to work stably in complex environments,and cell search is a key process of NB-IoT downlink receivers.Ensuring sufficient reliability and robustness in complex environments has become an impact device An important factor in performance.NB-IoT has been adaptively improved on the basis of Long Term Evolution(LTE)technology.Compared with LTE,it needs to detect all candidate sequences during cell ID search.Therefore,the NB-IoT cell search process is more complex.Based on the Narrowband Internet of Things communication protocol,this paper first studies the cell search algorithm based on coherent accumulation.By coherently accumulating the correlation calculation value of the retransmitted signal,the diversity gain is improved to ensure low signal noise.Reliability of synchronization signal correlation detection under the condition of ratio.Secondly,from the perspective of the amount of mathematical calculations,the algorithm complexity of the proposed scheme is analyzed.Finally,the NB-IoT baseband digital simulation platform is built based on Matlab.On this basis,the NPSS coarse synchronization and NPSS in the cell search algorithm based on coherent accumulation are analyzed.The simulation analysis of the fine synchronization and NSSS detection process verified that under the signal-to-noise ratio of-15?-10 d B,the method of coherent accumulation can effectively improve the accuracy of the estimation results of frequency offset and time offset,and meet the requirements of the NB-IoT downlink communication protocol.It compares the performance of parameter estimation and cell ID detection in the cell search process under different channel models,and investigates the average time consumption of the cell search algorithm.