how much power consumption in Mesh BT?

[Dennis.kim]

Hi,

I want to implement sensor data monitoring using Mesh BT.

I would like to predict the power consumption before implementation.

- If about 100 nodes are connected to Mesh, so how much current consumption is expected?

- is the mesh table maintained even when entering sleep mode?

- When in sleep mode, is it possible to wake up by other device BT signals?

  

Thank you all.

[tesc]

Hi,

The power consumption of a relay node is constant, as it needs to be in RX mode at all time when it is not doing TX, and RX and TX power consumption rates are comparable. For e.g. Low Power Nodes, power consumption depend on frequency of sending messages, and message size. You can investigate power consumption for a Bluetooth mesh Low Power Node through the Online Power Profiler for BLE, by checking BLE advertising with the frequency needed for containing the messages. (Bluetooth mesh payload is 11 bytes for a BLE TX payload of 31 bytes.)

Can you elaborate a bit, what you mean by "mesh table"? Bluetooth mesh is a flooding mesh, so there is no routing table. The state of a nodes models are persistent through power off or sleep. Relay nodes need to be online persistently. Low Power Nodes may sleep, and wakes up when needing to communicate with the network. There are Friend nodes (also persistently on, can be combined with Relay feature), that holds messages addressed to Low Power Nodes, so the Low Power Node can fetch messages when it wakes up.

The radio must be in RX mode for receiving incoming packets. The nRF52 series do not have conventional "sleep" states, rather the peripherals that are in use will be powered and the ones that are disabled will not be powered. See Power management unit (PMU). Similarly for the CPU. With the Programmable Peripheral Interconnect (PPI), for instance a timer can wake up the Radio peripheral for listening for incoming packets, and in the event of an incoming signal wake the CPU (otherwise reset the timer and go to sleep again.) PPI is used extensively by our BLE stack, in order to achieve low power consumption. For BLE, the radio wakes up for the BLE events at the right time. For Low Power Nodes in Bluetooth mesh, there is no timing and messages are polled from the Friend node. For other Bluetooth mesh nodes, they are always in RX or TX.

Regards,
Terje