Performance Evaluation of Chirp Spread Spectrum as used in LoRa Physical Layer

Abstract

Divergent modulation schemes have been proposed for Internet of Things (IoT). One specific application is sensor networks, where narrow band of data is required to be transferred for long distance and modulated signals are susceptible to interference. Chirps signals can traverse long distance and are resilient to White Gaussian Noise and Doppler effects. We analyze the performance of chirp spread spectrum as used in LoRa™physical layer for noise resilience. We evaluate Chirp Spread Spectrum (CSS) at ISM band 868 MHz for spreading factor 7 to 12 at bandwidth 125 kHz and sampling frequency 125Khz. Signals are transmitted through AWGN channel and are evaluated for Bit Error Rate (BER). Packet collisions and packet error rate were analyzed for simultaneous transmissions.