Design And Implementation Of Channel Tracking For LPWAN System Based On Narrowband ?/2-bpsk

The widespread application of the internet of things has promoted the rapid development of Low Power Wide Area Network(LPWAN)technology.The low power consumption and low cost requirements of LPWAN could lead to a big frequency offset between the LPWAN transmitter and receiver.And the terminal movement may cause doppler fading.These could affect the performance of LPWAN system.To deal with these problems,the new LPWAN technology Tur Mass uses ?/2-bpsk phase modulation and channel tracking method.For channel tracking based on narrowband ?/2-bpsk modulation,Tur Mass proposes design requirements from four aspects,which are frequency offset and doppler fading performance,signal-to-noise ratio requirements,robustness and DSP processing time.By evaluating the existing adaptive filtering algorithms,the Kalman filtering algorithm is selected as the design focus of the channel tracking scheme in this thesis.The ?/2-bpsk modulation has the property of constant envelope after a suitable sinusoidal pulse shaping filter,while the sinusoidal filter will cause inter-symbol interference of the system.The interference could affect the equalization and decision in the Kalman filter channel tracking,thereby reducing the channel estimated quality.This thesis eliminates the inter-symbol crosstalk in the ?/2-bpsk modulation communication system through interference cancellation.Based on the channel characteristics of the LPWAN system,three channel tracking based on Kalman filter are designed,which are Autoregressive(AR)model,Linear Trend(LT)model and Second Order Trend(SOT)model,respectively.In order to meet the design requirements of frequency offset and doppler fading performance,signal-to-noise ratio requirements,and robustness,corresponding tests are designed.A detailed simulation evaluation is made on the three channel tracking schemes with MATLAB.Finally,the channel tracking scheme based on the SOT model is selected as the DSP implementation scheme of channel tracking in this thesis.For the design requirements of DSP processing time,the channel tracking scheme based on the SOT model is implemented and optimized on the DSP,so that the actual test time of one frame of data is less than 0.12 ms,which meets the DSP processing time requirements of Tur Mass.Finally,it is concluded that all the design requirements are met.