Low-cost SDR-based Tool for Evaluating LoRa Satellite Communications

LoRa (Long Range) technology, with great success in providing coverage for massive Internet-of-things (IoT) deployments, is recently being considered to complement the terrestrial networks with Low Earth Orbit (LEO) satellite connectivity. The objective is to extend coverage to remote areas for various verticals, such as logistics, asset tracking, transportation, utilities, agriculture, and maritime. However, only limited studies have realistically evaluated the effects of ground-to-satellite links due to the high cost of traditional tools and methods to emulate the radio channel. In this paper, compared to an expensive channel emulator, we propose and develop an alternative method for the experimental study of LoRa satellite links using lower-cost software defined radio (SDR). Since the working details of LoRa modulation are limited to the reverse-engineered imitations, we employ such a version on SDR platform and add easily controllable adverse channel effects to evaluate LoRa for satellite connectivity. In our work, the emulation of the Doppler effect is considered as a key aspect for testing the reliability of LoRa satellite links. Therefore, after demonstrating the correctness of the (ideal)
$L$
oRa transceiver implementation, achieving a low packet error ratio (PER) with a commercial
$L$
oRa receiver, the baseband signal is distorted to emulate the Doppler effect, mimicking a real LoRa satellite communication. The Doppler effect is related to time-on-air (ToA), bounded to communication parameters and orbit height. Higher ToAs and lower orbits decrease the link duration, mainly because of dynamic Doppler effect.