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?

[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]

Simpler is better, absolutely. I think you can go for a connection oriented star or possibly a unidirectional or bi-directional connectionless star . In both cases go at least for a external antenna based module and optionally with a PA/LNA (as stated earlier the PA/LNA gives you some link budget and forgives bad placement decisions to some extent.

In a connection oriented star network:
The central point of the will be a Bluetooth central which connects to the Bluetooth peripheral sensors, the central will not be power efficient but the sensors on the edges can be battery operated. The connected Central can have upto 20 sensors that can be simultaneously connected, so you can choose to sample the sensors in a scheduled fashion or have a 3-4 Central nodes that will connect to the 70 odd sensors that you have. The links can be encrypted so data privacy is ensured.

Do a channel map management so the Centrals will get a different set of Channel maps each, additionally ensure that the channel maps do not collide with local WiFi.

In a connectionless star network:
The sensors are advertising as Bluetooth broadcasters and the gateway is a scanner. There is no data encryption so you need to implement an encryption scheme yourselves. It is simple for the sensors to be be battery operated and only broadcast (unidirectional), if you want to make the sensor bi-directional i.e. an advertiser and scanner role, you will have to work a bit more to do this in a battery friendly was but definitely possible (you will need to keep the scanner after the advertising and keep it as short as possible, if you dont control the scanner then it becomes the Bluetooth mesh role). In this case you will need only a single gateway to handle the connectionless advertising and scanning.

Make sure you have the link budget as at 300m you are at the limit of an external antenna solution, a PA/LNA will help here.

[vkadal]

Thanks for the detailed reply. The data flow is bidirectional. I need  to set some  limits for the sensor parameters. Can you suggest suitable modules for end devices and the central node?

[daviddedwin]

If you like my replies please give them upvotes.

If you are going for the connection oriented solution:
You can go for the nRF52840 based module with external antenna and optionally PA/LNA. The Central will need a lot of RAM to manage the links and the nRF52840 has the maximum RAM and FLASH. You can also choose to use a module with the nRF52833 IC as that has more RAM as compared to the nRF52832. The nRF52832 will be the most affordable IC as it has been in production the longest in the nRF52 series. The peripheral does not need a lot of RAM and FLASH so the nRF52832 should be fine as well, but since the project is small it may be simpler to pick a single module an use it for both central and peripheral.

https://www.nordicsemi.com/Software-and-Tools/3rd-Party/3rd-party-modules#shortrange ,  the ones with u.FL refer to the external antenna connector. Raytac has good availability in your region and you can check for other modules as well locally. You send me a direct message for more information.

[vkadal]

Thaks a lot for the inputs

[daviddedwin]

Please accept the answers that you liked the most and upvote them. Thanks for choosing Nordic.