nRF Bluetooth Mesh

[vkadal]

I have a requirement to collect data over a plant, say a power plant whose size may be 3 KM by 3KM. I am planning to  have a Bluetooth mesh and collect data and control equipments.  The collected data shall be given to the SCADA installed in their plant.

Can message / command hop and reach the final destination in a Bluetooth mesh?

What is the line of site range of Bluetooth devices?

Kindly suggest required development boards and Bluetooth devices so that I can arrange a demo to my client?

[Joakim Jakobsen]

Hi. 

There shouldn't be an issue to cover an area of 3km x 3km, as long as you have a sufficient number of nodes and relay nodes in the network.

As long as the network is covered by relay nodes (Relay nodes: Nodes in the network that will relay messages through the network, increasing range and coverage)  your message/command will be able to hop and reach the final destination.

Line of sight range of BLE / BLE Mesh nodes is very hard to say exactly. It will heavily depend on the environment, noise from other sources, obstacles, radio output power etc. 

If you want to make a demo for your client, you could simply use a network of our development kits. If you don't have any specific requirements of memory, peripherals etc. you could take a look at the nRF52832. 
We have working examples in our nRF5 SDK for Mesh that you can use as a starting point for your demo. 

Please let me know if you have any further questions. 

Br, 
Joakim Jakobsen

[daviddedwin]

Thanks for asking this question. 3KM by 3KM is a pretty large area and would increase the number of hops in the mesh to beyond significant levels, by signification I mean a hop count of more than 10. I would strongly urge you create zones in the mesh and also plan for a backhaul between the zones.

Each zone should have 100-200 nodes typically, the nodes per zone can be increased if your bandwidth requirements are very low but I would start at the suggested typical and then move to larger zones. You should have a backhaul between the zones like LoRAWAN or just Ethernet.
Each zone will need a zone controller that sits on the backhaul.

Line of sight range where both end points are visible, obstructions are not present , outdoor and the antenna performance is good can be about 100m even on 0dbm, you can also get better range when you switch the RF side to the CODED PHY (as opposed to standard 1Mbit PHY in the mesh spec), range using the same constraints stated earlier can be about 900m to 1km.

Additionally evaluate a external PA/LNA for the mesh which will get you better performance as compared to using the mesh on CODED PHY

You must control the relay nodes that are used for hopping very strictly so that you get the bandwidth that you need.

[vkadal]

Increasing the number of nodes to cover a larger area will increase the cost and complication. Simpler option,  for this use case, will be wired RS-485 . However thank you for the update

[daviddedwin]

Yes, a wired multi drop bus is always a possibility but

1. wireless reduces installation costs when  compared to a multidrop bus installation
2. adding a wired retrofit solution to a existing plant wiring is more complex and has more resistance in the plant management hierarchy, so a wireless retrofit is more amenable as it is seen as less disruptive
3. The value of a wireless solution is always perceived as more valuable, as the sales resistance to a wireless pilot project is less which results in more interested prospects

It does make sense to use wired and wireless as a mix and match, and a wireless component definitely adds more flexibility and value to the solution.

Some customers see wireless as a more reliable solution as opposed to a cable when cable wear and tear due to vibration, light or heat or movement etc is present.

Hope this helps

[vkadal]

Yes, I agree with the point of view. Now I have checked the distance between sensors. Now I understand all the sensors will be within a range of 200-300 meters. So Bluetooth mesh seems to be a good solution. 

I am planning to use ADXL series accelerometers. They have 3 analog outputs. So these tree inputs shall be measured and transmitted to a central  location.

Can you suggest me the exact part number to achieve this solution? The data can be delivered locally through RS-232 to any local laptop / desktop