3 ms·

Great project! Is there any mechanism implemented to ensure compliance with the EU regional limitations of the maximum duty cycle in the 868-870 MHz bands? ZigB

Great project! Is there any mechanism implemented to ensure compliance with the EU regional limitations of the maximum duty cycle in the 868-870 MHz bands? ZigBee can be quite chatty as it operates on the unrestricted 2.4 GHz bands.

johnwalkr 3y ago
I think this is handled by the radio modules or else they wouldn’t be certified, so you just have to make sure you don’t order a US-only module. FYI there is also a 2.4GHz version of Lora. It has very high sensitivity modes close to the performance of the sub-GHz version, but also has high performance modes that give you up to 2Mbps.
- retSava 3y ago
  Not necessarily. Often rf modules are pre-certified mostly to show that the hardware implementation and radio modulation and all that works as intended. Eg no spurious emissions, transmits at the freq you ask for etc. What gp asks for is that regulation requires either polite transmissions aka listen before talk aka clear channel assessment, ie before we send, listen for a while and back off if channel is busy. If LBT isn't used, there's a maximum allowed transmission duty cycle stated. Zigbee typically uses LBT, Lora doesn't. Hence, a clear zigbee channel may result in a very chatty lora channel. And another problem is the difference in bandwidth, where zb uses 250kbit/s at 2.4 GHz and a transmission may take on the order of a millisecond, Lora even on minimum spread takes hundreds of ms, on max spread a single transmission can take several seconds. This limits the scalability of lora networks in dense physical deployments. Lora primary use case is the once-a-day-ish sensor transmission.
  - snovv_crash 3y ago
    LoRa is also used in latency sensitive environments, eg. Crossfire, R9 and ExpressLRS for racing drone control links. This is even with LBT enabled.
ha_ru 3y ago
Yes, in fact we actually re-transmit the absolute minimum information (device join/sensor values) to ensure that the LoRaWAN link does not saturate. Data compression helps too and a user can also disable re-transmission of some meta-data, like link quality/battery level.

johnwalkr 3y ago

I think this is handled by the radio modules or else they wouldn’t be certified, so you just have to make sure you don’t order a US-only module. FYI there is also a 2.4GHz version of Lora. It has very high sensitivity modes close to the performance of the sub-GHz version, but also has high performance modes that give you up to 2Mbps.

retSava 3y ago
Not necessarily. Often rf modules are pre-certified mostly to show that the hardware implementation and radio modulation and all that works as intended. Eg no spurious emissions, transmits at the freq you ask for etc. What gp asks for is that regulation requires either polite transmissions aka listen before talk aka clear channel assessment, ie before we send, listen for a while and back off if channel is busy. If LBT isn't used, there's a maximum allowed transmission duty cycle stated. Zigbee typically uses LBT, Lora doesn't. Hence, a clear zigbee channel may result in a very chatty lora channel. And another problem is the difference in bandwidth, where zb uses 250kbit/s at 2.4 GHz and a transmission may take on the order of a millisecond, Lora even on minimum spread takes hundreds of ms, on max spread a single transmission can take several seconds. This limits the scalability of lora networks in dense physical deployments. Lora primary use case is the once-a-day-ish sensor transmission.
- snovv_crash 3y ago
  LoRa is also used in latency sensitive environments, eg. Crossfire, R9 and ExpressLRS for racing drone control links. This is even with LBT enabled.

ha_ru 3y ago

Yes, in fact we actually re-transmit the absolute minimum information (device join/sensor values) to ensure that the LoRaWAN link does not saturate. Data compression helps too and a user can also disable re-transmission of some meta-data, like link quality/battery level.