Terminal node emission signal Doppler pre-compensation method based on LoRa system

Abstract

The invention discloses a terminal node emission signal Doppler pre-compensation method based on a LoRa system, and the method comprises the steps: firstly analyzing a distribution function and probability density of the relative distance between a terminal and a satellite according to the distribution probability density of the terminal in an area; calculating the probability density of Doppler frequency shift of the terminal and the satellite according to satellite orbit parameters and a Doppler frequency shift calculation formula; secondly, establishing a Doppler frequency shift pre-compensation optimization problem for the randomly distributed terminal pre-compensation model in the region, and solving an optimal pre-compensation value of the system according to the optimization problemand a probability density function of Doppler frequency shift of the terminal and the satellite; to solve the problem of inter-carrier interference caused by a Doppler effect between a low-orbit satellite and unauthorized blind sending terminals distributed in a certain region range, theoretically deriving a relationship between a probability density function of distribution of the terminals in acertain region and average Doppler frequency shift of a system; the invention further provides a terminal node Doppler pre-compensation method, and the problem of inter-carrier interference of different sub-channel terminals in the system is relieved.

Description

technical field [0001] The invention relates to the technical field of wireless communication, and mainly relates to a Doppler pre-compensation method for a signal transmitted by a terminal node based on a LoRa system. Background technique [0002] In recent years, applications of the Internet of Things have gradually penetrated into daily life, such as shared bicycles, smart homes, and smart agriculture. With more and more application scenarios of the Internet of Things, traditional mobile communication technologies cannot be applied to all application scenarios. For places that cannot be covered by ground networks, such as forest fire prevention, earthquake monitoring, and resource development, satellite communication systems can be used for large-scale Internet of Things terminal data exchange. LoRa is one of the LPWAN communication technologies. It is an ultra-long-distance wireless transmission scheme based on spread spectrum technology adopted and promoted by Semtech C...

AI Technical Summary

Problems solved by technology

[0005] The common method of Doppler frequency offset estimation and compensation is to improve the wideband acquisition and large dynamic range tracking of the phase-locked loop, but it will affect the performance of other aspects of the system, such as increasing the complexity of the system, prolonging the signal acquisition time, etc.

Moreover, the blind direct connection terminal of the Internet of Things (asynchronous direct access to LEO satellites) cannot establish a closed-loop structure, and this method is not applicable

In the open-loop structure, it is a simple method to calculate the relative position and velocity between the satellite and the ground fixed receiving station based on Kepler's law, so that the Doppler frequency shift can be estimated in advance, but there are also some shortcomings: The amount of calculation is large in the pre-estimation, and the storage space required in the real-time compensation is large, and the receiving platform considered is only the fixed station on the ground

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