BRB Lora Overview
System Overview
High-power rocketry telemetry presents a dual constraint problem: maintaining reliable long-range communications while operating in an RF environment that may include dozens of simultaneous transmitters. Conventional single-channel or unsynchronized packet systems degrade under these conditions due to increased collision probability and receiver congestion. The BigRedBee LoRa GPS tracking system addresses both challenges through a time- and frequency-coordinated architecture designed specifically for dense launch environments.
Timing and Synchronization Architecture
At the core of the system is GPS-derived time synchronization. Each transmitter and receiver synchronizes its timing using the GPS pulse-per-second (1 PPS) signal, establishing a shared absolute time reference across all devices in the network. This eliminates long-term timing drift as a source of desynchronization and allows all communication events to be scheduled deterministically relative to GPS time.
Channel Access and Frequency Management
The system implements a pseudo-random frequency hopping sequence that is identically computed by both transmitter and receiver from shared parameters and the common GPS timebase. Because hop selection is deterministic, no over-the-air coordination is required. The receiver can therefore align its listening windows precisely to the expected channel at the expected time, minimizing idle scan time and improving acquisition reliability.
Time-Division Multiple Access
In addition to frequency diversity, the system incorporates time-slot scheduling within each one-second interval This design significantly reduces packet collision probability in crowded launch scenarios, where multiple transmitters may otherwise contend for identical RF resources.
Spectrum Deployment Considerations
The system supports operation in both the 900 MHz ISM band and the 70 cm amateur radio band. The availability of a 70 cm configuration provides an alternative operating environment for licensed users, enabling frequency flexibility at large launches where 900 MHz congestion may be present due to widespread adoption of ISM-band tracking systems.
System Outcome
The combination of GPS-disciplined timing, deterministic frequency hopping, and time-slot multiplexing yields a telemetry system that scales with increasing transmitter density while preserving long-range performance. Rather than relying on increased transmit power or simplified single-channel links, the architecture addresses interference at the protocol level, enabling consistent performance under realistic launch-day RF conditions.
