Wireless links have traditionally forced a trade-off between speed and range. High-throughput technologies such as Bluetooth and Wi-Fi can move large amounts of data quickly, but their practical range is often limited. Long-range technologies can cover much greater distances, but typically at lower data rates. Fast Long-Range Protocol (FLRP) burst is designed for the gap between these two worlds: a kilometer-class range with megabit-per-second data transfer.
FLRP burst is a high-throughput wireless transfer protocol built on the Fast Long-Range Communication (FLRC) physical layer (PHY). It combines a low-power LoRa® Wake-on-Radio (WOR) mechanism with a high-speed FLRC data burst. The result is a link designed to sustain high data rates over long distances while keeping the radio active for as little time as possible.
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Protocol |
FLRP Burst |
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Physical Layer (PHY) |
LoRa |
FLRC |
LoRa and FLRC each handle what they do best:
The FLRP burst's value isn't in range or throughput on its own — it's in the combination of letting devices move images, logs, diagnostics, or firmware without keeping a high-power radio active for long.
FLRP burst separates the low-power discovery and synchronization phase from the high-speed data phase. The receiving device remains in a low-power listening state until the initiator starts an exchange. Once the link is established, FLRP burst selects suitable radio conditions and moves the payload using short FLRC bursts.
The initiator sends a long-preamble LoRa WOR signal sized to cover the receiver's sleep period. The receiver detects the preamble during a routine CAD check, verifies the target Device Extended Unique Identifier (DevEUI) and replies. This exchange establishes the timing and frequency alignment needed for the FLRC burst.
The transmitting side can probe up to 16 enabled channels. The receiver measures Received Signal Strength Indicator (RSSI) and frequency offset and selects an appropriate channel and data rate for the burst. This adaptive step can also be disabled or limited to channel selection or data-rate selection.
Payload data is transferred as back-to-back FLRC packets, with each burst capped at 400ms. If a payload is larger than the selected data rate can fit into that window, FLRP burst splits it into consecutive bursts. Each burst has its own acknowledgment (ACK) and retry cycle. Only packets confirmed missing by the receiver are retransmitted.
When cryptographic integrity is enabled, every packet carries an Advanced Encryption Standard Cipher-based Message Authentication Code (AES-CMAC) message integrity code in place of the radio's standard Cyclic Redundancy Check (CRC). The receiver validates the code before accepting the payload. This provides packet-level integrity and authentication against modification or spoofing; it should not be confused with payload encryption.
Consider a battery-powered camera with a passive infrared (PIR) sensor. Most of the time, the node can remain in a low-power listening state. When the sensor detects an event, the camera captures a snapshot or short clip and sends it to a gateway.
This is where the combination of range, throughput, latency, and energy efficiency matters. The link must reach the gateway over a potentially long distance. It must also move a relatively large payload quickly. With FLRP burst, the high-speed FLRC burst can reduce transfer time and latency, while WOR and CAD keep the radio in a low-power state between events. Because each alarm is sent in a brief, high-rate burst with very little time on air, the node draws almost no energy per event — enabling multi-year battery life even at long range.
The FLRP burst bidirectional model supports firmware and configuration downloads to field-deployed sensors. Per-burst acknowledgment and selective retransmission help complete large transfers over imperfect links. Optional packet-level integrity checking can reject corrupted or modified packets before they reach the application layer.
For sensor-to-gateway uploads, WOR and CAD reduce idle listening overhead. When data is available, the device can move larger payloads in a short burst rather than keeping the radio active for a long, low-rate transfer. This is useful for batched measurements, diagnostic logs and other data that does not fit comfortably into a low-data-rate link.
The FLRP burst is designed to close a gap between high-throughput short-range wireless and low-rate long-range connectivity. It combines LoRa WOR and Channel Activity Detection with high-speed FLRC bursts to target megabit-class data transfer at kilometer-class range.
The benefit goes beyond peak throughput. Higher data rates can shorten time on air, reduce transfer latency and reduce the time the active radio path must remain powered. Combined with low-power listening between transfers, this architecture can improve the energy efficiency of large-payload transfers and extend battery life.
For applications such as battery-powered security cameras, the result is a link designed to deliver images and short clips quickly, over long distances, without requiring continuous high-power listening. The LR2021 provides the foundation for this approach today.
The code, demos and documentation above provide a starting point for evaluation. Talk to our team about how FLRP burst on the LR2021 fits your application. While this overview focuses on the LR2021, FLRP burst also runs on other Semtech radios, including the SX1280/SX1281.
FLRP burst is a high-throughput wireless transfer protocol built on the Fast Long-Range Communication (FLRC) physical layer. It combines a low-power LoRa WOR mechanism with a high-speed FLRC data burst, designed to sustain high data rates over long distances while keeping the radio active for as little time as possible.
LoRa and FLRC each handle a different part of the job. LoRa's WOR phase aligns the link in frequency and time before the burst and carries the signaling that sets up and adapts each exchange, using its range and robustness to optimize the link to the highest possible data rate. FLRC then delivers the actual payload at high speed once the link is established.
FLRP burst supports adaptive per-exchange PHY rates from 0.26 to 2.6Mbps, with up to 1.7Mbps payload throughput within the data burst. It can achieve more than 1 Mbps payload throughput at kilometer-class range for both Sub-GHz and 2.4GHz frequency plans.
Between exchanges, the receiver can use LoRa Channel Activity Detection (CAD) instead of continuous receive mode — with one CAD check per second, idle current drops to roughly 100µA. Because the high-speed burst itself is short, devices spend very little time with the high-power transmit or receive path active, which helps extend battery life.
Each burst has its own acknowledgment and retry cycle, and only packets confirmed missing by the receiver are retransmitted — so an interrupted transfer doesn't require resending the whole payload. When cryptographic integrity is enabled, every packet carries an AES-CMAC message integrity code that the receiver validates before accepting the payload, protecting against modification or spoofing (this is separate from payload encryption).
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