Abstract:LoRa-based non-terrestrial networks are rapidly becoming infrastructure for global IoT, with LEO satellites delivering direct-to-device connectivity and drone-mounted gateways serving precision agriculture, emergency response, and environmental monitoring. Both settings share a fundamental MAC-layer bottleneck: large coverage footprints cause thousands of devices to collide on the same channel, while gateway mobility induces rapid link variations, making link-unaware transmissions a persistent source of wasted airtime. These challenges demand random-access solutions, yet ALOHA provides no collision coordination, CSMA sensing fails beyond ~15 km, and BSMA's continuous busy tone consumes 80-90% of the channel capacity. We propose Free Signal Multiple Access (FSMA), a synchronization-free, gateway-controlled MAC protocol. Like a traffic signal, FSMA uses a single LoRa upchirp (FreeChirp) to indicate channel availability. By transmitting it at a lower spreading factor than the node uplink, FSMA implicitly filters weak-link nodes through channel reciprocity, reducing the collision window by 6-200x without synchronization, handshakes, or hardware modifications. Hardware experiments with 25 COTS LoRa nodes and a drone-mounted gateway demonstrate 2x higher throughput, 2.5-5x better packet reception ratio, and up to 5x improved energy efficiency. Large-scale simulations with real TLE-based satellite trajectories confirm scalability to 5000+ devices per satellite pass.
From: Rohith Reddy Vennam [view email]
[v1]
Fri, 3 Oct 2025 08:18:25 UTC (13,671 KB)
[v2]
Wed, 9 Sep 2026 09:44:32 UTC (13,593 KB)
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