What is LoRa, and is it used in industrial remote control?
LoRa is a sub-GHz modulation using chirp spread spectrum; it excels in telemetry, but its latency makes it unsuitable for real-time motion control.
LoRa is a sub-GHz modulation that uses chirp spread spectrum (CSS) and can resolve a signal below the noise floor. It is outstanding in telemetry but unsuitable for real-time motion control: the price is a very low data rate and a high air time. What is decisive on a crane or a hydraulic lever remote control is not range but latency, and LoRa is weak on exactly that side.
Where the sensitivity advantage comes from
While the typical ceiling on FSK receivers is -125 to -130 dBm, LoRa goes significantly below that at low rates; on the SX1276 a sensitivity down to -148 dBm is reported at the lowest data rate, and around -137 dBm at practical rates. At the most extreme setting an advantage of roughly 25 dB over FSK is reported, and by the 6 dB rule that means, theoretically, a very large difference in distance. The source of the gain is not magic: the signal is spread out in time, and the receiver gathers that spreading back up to obtain processing gain. In other words range is bought directly with time, and in a remote control application that trade works against you.
What is decisive in a remote control is latency
- At high spreading factors the air time of a single packet reaches hundreds of milliseconds; the delay between the operator releasing the lever and the movement stopping becomes unacceptable.
- Long air time fills the duty cycle limits quickly. A duty cycle of 1 percent means a total of 36 seconds of transmission per hour; a remote control sending continuous commands uses that up in a short time.
- Safety functions have to be fast and deterministic; a slow channel with variable latency makes that difficult.
Where it suits and where it does not
| Application | LoRa | Decisive reason |
|---|---|---|
| Remote sensor, level, meter | Suitable | Infrequent and small data |
| Position and status reporting | Suitable | Latency is not critical |
| Alarm and fault reporting | Conditional | Acceptable if one-way and infrequent |
| Crane motion control | Not suitable | Continuous commands, low latency required |
| Proportional control on a hydraulic lever | Not suitable | The joystick response has to be immediate |
A common misconception
The reasoning “LoRa has a long range, so my remote control will reach further” does not hold in the field. The setting that increases the range also slows the response down; and when you raise the rate and bring the latency down, the sensitivity advantage largely melts away. For a remote control the right question is how much of the range receiver sensitivity actually explains — the noise floor, the antenna placement and the obstacles are more decisive on most sites. The second misconception is to take the range figure of the module for the range of the system; between the two there are the antenna, the housing and the mounting. The sensitivity values in the data sheet are the manufacturer's declaration under laboratory conditions and do not explain the field result on their own; that is why the decision is made not with the data sheet but with the stopping delay you measure on your own installation.
The decision rule is this: if the data is infrequent and the latency is not a concern, consider LoRa. If the machine moves while the operator holds a lever, do not consider it; for that job low-latency FSK/GFSK or frequency hopping solutions are preferred. If you are thinking of converting an existing system to LoRa, first measure the time between releasing the button and the movement stopping on the present installation, and build the decision on that number. If the time you measure is going to grow on the new channel, you will have narrowed the operator's window of reaction in return for the range you gain.
The full topic: Wireless remote control installation: pairing, relay, safety