Design And Implementation Of Beacon Signal And Acquisition Scheme For A New Type Of LPWAN System

The nowadays LPWAN technology has problems such as insufficient network capacity,low access success rate,and complex protocols when facing the access demand of massive terminal devices.Tur Mass,a new LPWAN technology based on grant-free random access with massive MIMO,utilizes frequency division multiplexing and space division multiplexing to significantly increase the network capacity of the system.For the beacon signal and acquisition scheme,the Tur Mass system proposes 9 design requirements such as signal bandwidth,modulation type,acquisition sensitivity,maximum acquisition time delay,etc.This article designs the beacon signal and capturing scheme to fulfill these system requirements.Aiming at the requirements of Tur Mass system,a beacon signal based on random search sequence and modulated by GMSK is designed.Compared with the traditional m sequence,Gold sequence and ZC sequence,the beacon signal generated by this sequence has good autocorrelation in the time domain,and also has good autocorrelation in the frequency domain.In addition,simulations verify that the anti-interference ability of the beacon signal modulated by GMSK is significantly better than that of MSK modulation.In this thesis,a frequency offset-parallel beacon signal acquisition scheme and a time offset-parallel beacon signal acquisition scheme based on FFT is designed.Through simulation verification,the frequency offset-parallel acquisition scheme based on FFT has basically the same performance when the computational complexity is 70% of the time offset-parallel beacon signal acquisition scheme,and the maximum acquisition time delay is much lower.Using the hardware architecture of DSP+FPGA+MCU,a test platform for the beacon signal and acquisition scheme of the Tur Mass system is built.This paper has carried out tests on the acquisition sensitivity,anti-interference and frequency offset.When the received signal power is-142 d Bm,the acquisition success rate is higher than 99%.The antiinterference ability is also higher than 49 d Bc.The results show that the solution in this paper can fully work in the actual LPWAN scenario,and fulfills all the 9 design requirements.In summary,this article has completed the design of the beacon signal and acquisition scheme in response to the needs of the Tur Mass system.The simulation and test results show that the beacon signal and acquisition scheme designed in this article fully meets the design requirements of the system,which is a good solution for the beacon signal and acquisition scheme of the Tur Mass system.