Hi, is there a tutorial document available for multicast, please?
HI. Multicast from where? BuildIn or external NS+AS? For external you can read here: https://www.chirpstack.io/network-server/features/multicast/
For BuildIn NS and AS in RAK Industrial Gateways, for now is not implemented.
Could you share me the c code sample for the RAK811 to receive Multicast message, thank you.
What do you mean about Multicast message? Is it the LoRa P2P message not LoRaWAN?
I mean from LoRaWAN send multicast payload to all RAK 811 to make control at one command. Due to unicast to control each Lora end device will takes long time so multicast is must need. I understand in the gateway side can send multicast payload from external API command? So from end device side should already have code to receive multicast from gateway?
Unless your nodes are mains powered, it is going to be very hard to achieve downlink in a short period of time. Battery powered nodes can only receive message during the small fraction of time they are awake and running the receiver, which typically costs 1000 times the power of their idle standby mode.
A multicast scheme could potentially let you schedule specific periods of time when all of the nodes that have recently communicated with the server would be running their receivers to collect any multicast messages, but you still face limitations in how often you can do that.
What power source is available for your nodes? What is the maximum acceptable latency for the first attempt to send the downlink? How do you plan to handle nodes which miss the first attempt?
This node is proposed using in the ceiling light in the car park. They are connected with main power. The ideal is the lights are dimmed until it sensing movement it then Quickly to send a msg to LoRaWAN gateway, then gateway send a multicast msg to relevant groups of lights to turn on. The delay in few seconds will significantly affected to user experience, as consider the car driving speed in the path. We also proposed using indicators light to lead the car to a parking spot, while the car entering. We plan in gateway resend the multicast msg regardless end node has received or not, so the speed for communication in both way are important.