Research And Implementation Of Narrowband Physical Uplink Shared Channel In NB-IoT System

The Narrow Band Internet of Things(NB-IoT),based on cellular communication,is an emerging narrowband radio technology that offers advantages in terms of enhanced coverage and mass access compared to 4G technology for humans.However,how to efficiently use limited spectrum resources to enhance coverage and reduce interference is a key issue in the NB-IoT Narrowband Physical Uplink Shared Channel(NPUSCH).The thesis is based on industry-specific major topic “NB-IoT IoT Terminal SOC Development and Application” and the cooperation project with the 41 st Research Institute of China Electronics Technology Group Corporation "ZYNQ-based NB-IoT test equipment development",and the corresponding solution in the transmission and reception process of NPUSCH is given and implemented.At the same time,under the premise of less interference and high spectral efficiency,a method of reserving the guard band is adopted to improve the energy efficiency of the NPUSCH.The main research contents and innovations of this thesis are as follows:1.The process of the NPUSCH signal processing transmitter is briefly introduced.The important modules in the receiving process are described and analyzed in detail to show how to receive at the Base Station(BS).The time-frequency structure of Narrowband Demodulation Reference Signal(NDMRS)is analyzed and simulated.The simulation results show that in NPUSCH format 2,the number of symbols transmitting NDMRS in each slot increases from 1 symbol to 3 symbols with 2dB performance gain;based on the NPUSCH link,the channel estimation of NPUSCH is done through the Least Square(LS)algorithm and the Linear Minimum Mean Square Error(LMMSE)algorithm,respectively.The simulation results show that LS has 1.2dB performance loss than LMMSE algorithm,but its structure is simple and easy to implement.A selection method for the number of repeated transmissions of NB-IoT is proposed.The simulation results show that the performance gain of 2dB can be obtained by one repeated transmission,and the performance can be better and the spectrum efficiency is higher by selecting the optimal number of repeated transmissions.2.The orthogonality of the system is disrupted due to the difference in subcarrier spacing,causing mutual interference between systems,which may result in severe degradation of system performance.In this thesis,the NPUSCH of NB-IoT system interfered by other network systems is studied and simulated,and the performance of NPUSCH under adjacent frequency interference is studied and analyzed.The simulation results show that when NB-IoT BS Adjacent Channel Selectivity(ACS)reaches 40 dB,the Signal Noise Ratio(SNR)loss of the NB-IoT system is less than 1 dB.In order to improve the energy efficiency of the NPUSCH,a method of reserving the guard band is adopted to avoid the interference of the Narrowband Physical Random Access Channel(NPRACH),and the energy efficiency can be increased by 1.74 times when the guard band reaches 15 kHz.3.In order to meet the project requirements,this thesis implements the NPUSCH link module on TI's TMS320C6670 Digital Signal Processor(DSP).The Bit Error Ratio(BER)performance of MATLAB simulation and DSP implementation is compared.The NPUSCH is discussed based on performance and operational efficiency,which proves that the proposed scheme can meet the project requirements.