LoRa調變中符號錯誤率之研究

Abstract

遠程（LoRa）調變系統採用線性調頻展頻（CSS）技術，旨在提供低功率和寬範圍的通信範圍（半徑可達數公里）。即當設備選擇展頻因子（SF）時，通過以與2𝑆𝐹成比例的速率掃描整個頻寬來發送每個符號。在接收處，首先使用去線性展頻信號去除接收信號的CSS部分，然後使用離散傅里葉變換（DFT）提取符號中包含的信息。本論文計算了LoRa調變系統的符號錯誤率。如將要說明的，當N-1個獨立瑞利隨機變量的最大值大於獨立萊斯隨機變量時，會出現符號錯誤，其中N是DFT中點的數量。與相關工作相比，從 MATLAB 仿真中獲得的數值結果顯示出很高的準確性。

A chirp spread spectrum (CSS) technique is adopted n a long range (LoRa) modulation system, which aims at providing low power and a wide range of communication range (of radius up to several kilometers). That is, when a spread factor (SF) is selected by a device, each symbol is sent by sweeping the entire bandwidth under a rate proportional to 2𝑆𝐹. At the receiver, a de-chirp signal is first used to remove the CSS part of the received signal and the discrete Fourier transform (DFT) is then employed to extract the information contained in the symbol. In this thesis, the symbol error rate of a LoRa modulation system is calculated. As will be illustrated, a symbol error occurs when the maximum of (N-1) independent Rayleigh random variables is larger than an independent Rician random variable, where N is the number of points in the DFT. Numerical results obtained from MATLAB simulations show great accuracy, as compared to related works.