Suggestion for Setting up a Mesh Network

[Usama Masood]

Any idea how large a surface we're talking about here? How many hops would be needed to go from one end of the network to the other?

Expected floor area is roughly 8,000 - 10,000 sqm

[ESP_Sprite]

Hm. I'd personally roll my own protocol then, based on ESP-Now, and without an actual mesh. If you can have a few (like 10? depends on RF conditions I guess) nodes that are connected to a backhaul of some sorts (Ethernet, perhaps WiFi via a 2nd ESP32) you technically don't need store-and-forward as all nodes can talk directly to one of the backhaul nodes. You don't seem to need a low latency, so you could do some sort of time division multiplexing: the backhaul divides a timeframe (e.g. 10 seconds) into e.g. 400 slots of 25mS each. Each slot allows only a small set of nodes (e.g. 10) to respond with their status (thus making sure there's little chance of collisions). At the beginning of each slot, the backhaul node broadcasts a status request packet, indicating which nodes are to respond, and if a request is pending it'll also send that. Once a node has responded with its status, it knows it won't have to do anything for the next 10 seconds, so it can shut down its radio for that duration. You can put the backhaul nodes on different channels, so they won't interfere with eachother.

[chegewara]

We also need to conserve the power as much as we can, that is why we are thinking more in terms of BLE
In current setup backend<->edge communication is over MQTT, and edge node translate the messages between MQTT to mesh

Im not sure you will get lower power consumption with ble mesh, since every node is doing ble scan for 99-100% of the time.
Unless you are planning to use ble mesh low power nodes (which i doubt, based on your description). I am also suggesting to read this long, but informative topic
https://github.com/espressif/esp-idf/issues/947

If i would work on such project i would make sure that ble mesh node is really much better in terms of power consumption before i go this way. Maintaining such a big ble mesh is challenging task:
- ble mesh edge nodes vs mqtt wifi routers
- ble mesh provisioning vs mqtt painless wifi provisoning
- ble mesh limit of nodes vs mqtt limitless
- ble mesh relays

It all depends if you can cover area with wifi routers or not.
As much as i love esp32 and i will suggest to use it in most of the project, when you want to build battery powered ble device nordic nrf528xx may be better in terms of power consumption. (sorry espressif, but it is still true)

[Usama Masood]

Thanks all for you suggestions, we will try these and update the thread with our findings