Research And Implementation Of NB-IoT System Synchronization Detection

In September 2015,the 3rd Generation Partnership Project(3GPP)announced the formalization of the Narrowband Internet of Things(NB-IoT)standard.In addition,they proposed a set of standardsf for the capabilities of NB-IoT system,including low-power,wide-coverage,support for mass connectivity,and flexible time delay.Synchronous detection is a prerequisite for establishing a communication link between a terminal and a base station.During the communication process,regardless of whether the terminal device is just powered on or the cell is switching,a connection must be established with the base station through the synchronization process.On the basis of the physical layer technical characteristics of NB-IoT system,this paper introduced the symmetrical design concept and the Zadoff-Chu(ZC)sequence used in the synchronization signal.Moreover,we explored detection algorithms for the NB-IoT system primary synchronization signal(NB-PSS)and NB-IoT system secondary synchronization Signal(NB-SSS).Finally,simulations were performed to verify the feasibility of the algorithms.To develop an NB-PSS detection algorithm,we analyzed the sequence structure and sequence mapping methods of NB-PSS and proposed an improvement to the matching filter detection scheme proposed by Qualcomm.Because the NB-PSS is mainly used for the synchronization of time and frequency in NB-IoT system,the performance of the improved NB-PSS detection algorithm directly affects the detection of NB-SSS.To detect the NB-PSS,we exploited its repetitive characteristics in the time domain,and calculated the variance of the correction valve thus substantially enhancing the detection accuracy for the NB-PSS.For the NB-SSS sequence,we first analyzed the sequence structure and the mapping method;then,we evaluated existing detection algorithms and proposed an algorithm based on the symmetric characteristics of the sequence to further reduce the complexity.Because the NB-SSS contains information regarding 504 cell IDs and NB-IoT systems require low power consumption,the complexity of the detection algorithm should be minimized.Therefore,based on the original algorithm,we utilized the symmetrical structure of the signal to improve the performance of the algorithm and reduce the complexity of correlation operation.