Open-Source 2.4 GHz Radio Breaks LoRa’s Data Bottleneck for Volcano Telemetry

A team of engineers in Peru has unveiled a fully open-source wireless transceiver that promises to shatter one of the most stubborn bottlenecks in remote scientific monitoring: the inability of sub-gigahertz LoRa radios to carry continuous, high-resolution data streams over multi-kilometre distances. The platform, called OpenFLRC v1.0, pairs a Semtech SX1280 transceiver operating at 2.4 GHz with an ESP32-S3 microcontroller on a custom carrier board, and it sustains an effective data throughput of 884.3 kilobits per second with a packet delivery ratio of at least 99.9 percent under laboratory testing. That figure is roughly thirty times the ceiling of the sub-gigahertz LoRa modules that dominate low-cost long-range telemetry today, and it comfortably exceeds the 115,200 bits per second serial ingestion rate demanded by high-resolution seismic instruments.

The motivation comes from a very concrete problem. Volcano observatories, seismic networks, and geophysical stations in regions without cellular or wired infrastructure need radio links that can carry uninterrupted sensor data across ten to twenty kilometres. A triaxial seismometer sampling at 200 samples per second with 24 bits per axis generates a raw stream of 14.4 kilobits per second, but telemetry protocols and encapsulation overheads such as MiniSEED formatting standardise on a 115,200 bits per second serial interface at the sensor output. To prevent buffer accumulation, the wireless link must sustain goodput at or above that serial speed. LoRa, the proprietary chirp spread spectrum modulation that has become ubiquitous in smart agriculture and volcanic monitoring networks, simply cannot deliver: at the high spreading factors required for robust long-distance links, its effective air rate collapses to one to five kilobits per second, making continuous high-rate streaming fundamentally impossible.

The research team, affiliated with monitoring efforts around the active Misti and Sabancaya volcanoes in southern Peru, validated the throughput limitation empirically. In comparative benchmarks against commercial Ebyte E22 modules at 433 MHz and 915 MHz, both sub-gigahertz LoRa systems saturated at a maximum sustained goodput of just 29.38 kilobits per second, enforced by a physical packet inter-arrival floor of 65.35 milliseconds. That is a shortfall of nearly four times against the 115.2 kilobits per second target, meaning such links can carry a 100-samples-per-second seismic stream but cannot handle a 200-samples-per-second stream with any robust margin. Previous work on the 16-kilometre Misti–Arequipa path had already confirmed the geometric feasibility of the radio link while highlighting exactly this throughput wall.

OpenFLRC’s answer is to move to the 2.4 GHz industrial, scientific and medical band and exploit FLRC, or Fast Long-Range Communication, a modulation mode native to the SX1280 transceiver family. In its fastest configuration, FLRC achieves a 1.3 megabit per second air rate with a receiver sensitivity of minus 97 dBm, sufficient for multi-kilometre links. The team’s carrier board integrates an Ebyte E28-2G4M27SX radio front-end delivering up to 27 dBm, or 500 milliwatts, of output power through a Skyworks power amplifier, alongside an ESP32-S3 dual-core microcontroller running at 240 MHz with 16 MB of flash and 8 MB of PSRAM. Crucially, the design grants users bare-metal control over the radio, exposing internal hardware buffers, explicit transmit and receive timings, and direct SPI interrupts through a custom C++ library, a level of deterministic control that closed commercial LoRa modules abstract away entirely.

The engineering details reveal why the platform performs as it does. Driving a 500-milliwatt power amplifier continuously under high-rate streaming draws rapid current pulses peaking at 550 milliamperes with nanosecond-scale rise times, which would destabilise a typical breadboard or prototype supply. The carrier board embeds a five-capacitor decoupling ladder directly adjacent to the radio module’s power pins: two 150-microfarad low-ESR tantalum capacitors acting as a local bulk energy reservoir, in parallel with three high-frequency X7R ceramic capacitors. A continuous 1-ounce copper ground plane on the board’s underside, stitched to the module with thermal vias, acts as a passive heat spreader for the roughly 1.3 watts dissipated as heat during full-power transmission. The board also routes the radio’s transmit and receive enable lines through dedicated low-capacitance traces, allowing the firmware to switch the RF front-end deterministically within 2.5 microseconds and preventing destructive amplifier reflections during transmit-to-receive turnarounds.

The firmware architecture is equally deliberate. Under FreeRTOS, the dual-core processor divides labour asymmetrically: Core 0 ingests the incoming 115,200 bits per second serial stream into a lock-free circular ring buffer in RAM, while Core 1 runs a dedicated radio scheduler that fetches 117-byte chunks and pushes them to the SX1280’s FIFO over an 18 MHz SPI bus with direct memory access, shrinking each payload transfer to roughly 56 microseconds. Radio state transitions are governed strictly by a hardware interrupt that triggers a RAM-cached fast interrupt service routine, eliminating the scheduling jitter that plagues polling-based designs. The team’s timing budget analysis shows a minimum theoretical packet cycle of 840.9 microseconds, and the empirical benchmark achieved 884.3 kilobits per second of goodput at a one-millisecond packet interval, corresponding to a 73.1 percent channel efficiency relative to the raw 1.3 megabit per second air rate. Notably, 82 percent of Core 0’s processing capacity and more than 470 kilobytes of SRAM remain free for user data acquisition and edge signal processing.

Validation was conducted with unusual rigour for open hardware. Rather than relying on uncontrolled over-the-air tests, the team built a conducted radio-frequency bench using a calibrated chain of SMA attenuators totalling up to 145 decibels of path loss, characterised segment by segment with a NanoVNA vector network analyser at 433 MHz, 915 MHz, and 2.44 GHz. This approach isolates true receiver sensitivity and firmware behaviour from the multipath fading, interference, and antenna pointing errors that make field measurements irreproducible. In attenuation sweeps, the sub-gigahertz LoRa links sustained near-unity packet delivery up to 130 decibels of conducted path loss, while the 2.4 GHz FLRC link held a 96.2 percent delivery ratio at 125.8 decibels before failing completely, a roughly five-decibel penalty consistent with the higher noise bandwidth of FLRC compared to narrow-band chirp spread spectrum.

Spectral measurements with a TinySA Ultra analyser confirmed the platform’s regulatory compliance. The occupied bandwidth measured between 1.336 and 1.347 megahertz across three operating channels, closely matching the configured FLRC parameters, and second-harmonic suppression ranged from 38.5 to 41.8 decibels below the carrier, comfortably within FCC Part 15.247 and ETSI EN 300 328 emission limits. The power control loop proved highly linear across an 18-decibel dynamic range. Link-budget emulation for the 16.4-kilometre Misti–Arequipa volcanic corridor, based on the ITU-R free-space model and the empirical sensitivity thresholds, indicates the link can theoretically close at that distance, though the authors recommend upgrading to 19 dBi parabolic grid antennas or adding an intermediate repeater to maintain a proper fade margin for field reliability.

The trade-offs are candidly acknowledged. The 2.4 GHz band incurs a 7.9-decibel free-space path loss penalty compared to 915 MHz, making the system dependent on line-of-sight conditions, and continuous full-power transmission demands careful thermal management in any field enclosure. The v1.0 firmware implements dedicated point-to-point streaming only, with multi-node contention protocols and the SX1280’s built-in time-of-flight ranging engine reserved for future releases. Yet the regulatory picture favours the chosen band: sub-gigahertz spectrum is fragmented regionally and subject to duty-cycle limits as low as 0.1 percent in Europe that legally prohibit continuous telemetry, whereas the 2.4 GHz band is globally harmonised with no duty-cycle restrictions, and rain attenuation over a 16-kilometre path is negligible at these frequencies.

Perhaps most striking is the price and accessibility. Each complete transceiver node costs 32.70 US dollars, built from commodity modules and a two-layer printed circuit board, and the entire project, including schematics, gerber files, firmware, bill of materials, calibration data, and benchmark videos, is published under a Creative Commons Attribution 4.0 license and certified by the Open Source Hardware Association under UID PE000005. For research groups monitoring volcanoes, earthquakes, or any high-rate phenomenon in infrastructure-poor regions, OpenFLRC demonstrates that the era of choosing between long range and sufficient bandwidth may finally be ending, and that a thirty-dollar open board can do what expensive proprietary telemetry systems have long monopolised.

Subject of Research: Open-source 2.4 GHz FLRC wireless transceiver hardware for high-throughput, low-latency continuous scientific telemetry

Article Title: Open-source SX1280 2.4 GHz FLRC transceiver: Overcoming sub-GHz LoRa bottlenecks for high-rate, low-latency continuous telemetry

Article References: Choquepuma, K. J. C., Rodriguez, K. E. A., Arenas Mamani, F. A., & Hilario-Tacuri, A. (2026). Open-source SX1280 2.4 GHz FLRC transceiver: Overcoming sub-GHz LoRa bottlenecks for high-rate, low-latency continuous telemetry. HardwareX, Article e00848. https://doi.org/10.1016/j.ohx.2026.e00848

Image Credits: AI Generated

DOI: 10.1016/j.ohx.2026.e00848

Keywords: OpenFLRC, SX1280, FLRC modulation, LoRa bottleneck, wireless telemetry, volcano monitoring, seismic networks, ESP32-S3, open-source hardware, 2.4 GHz ISM band, packet delivery ratio, HardwareX