BLE Mesh Network

[Tai]

Hi all,

I need to send the information from 2-5 sensors in a room. The sensors are placed 2-3 meters far from each other. Each sensor has a BLE, using a battery and generates about 20 bytes every 100 milliseconds. The sensors could be more than 20 in the future.

I would like to know the best approach for sending data from sensors to a smartphone regarding power consumption and the number of sensors that I need to use.

1- Using each sensor as a peripheral and connecting them separately to the smartphone.

2- Using the BLE of one sensor as a hub and passing all data through this BLE to the smartphone. Is it possible to be central for the sensors and be peripheral for the smartphone simultaneously?

3- Using a BLE mesh. Is it possible to send all data to the smartphone by using a mesh network?

I would really appreciate if someone could help me to choose the best option.

[endnode]

You will find all answers after few minutes of googling and searching here on the forum (and Nordic infocenter documentation), but here you go:

1. You can do that but most of the phone/tablet/PC devices won't be able to maintain 20 BLE GAP Central connections at a time. So if you insist on 100ms reporting time then you will need some aggregator or "store and forward" mechanism.
2. It's indeed possible to operate BLE device with several connection links and they can have different GAP roles (Peripheral/Central). Just Nordic BLE stacks on nRF52 chips support up to 20 concurrent connection links and there are other stacks which claim to support even more.
3. Oh yes, here we go, mash everywhere, nice buzzword, put it wherever you can;) Yes, IF you can make the mesh network working in order to transport the data streams (20B per device every 100ms) you will still have problem how the smart phone connects to it. As far as I know BT SIG mesh (if you mean this one, there are many proprietary attempts to define such working scheme - but the story on smart phones is the same) works on top of BT LE GATT layer but all the smartphone apps I've seen (mainly Android, is there any iOS app released yet?) are just for provisioning and network configuration. I guess they might work as normal relay/node as well but giving a nature of BLE mesh operation (connecting for a short time to random nearby nodes) I don't see how this could handle your use case.

If you see most of the commercial things with multiple sensors (typically weather stations/smarthome hubs/home security systems) are using single "hub" which connects to the nodes and makes all upstream communication to backend (WiFi) or user app on the smart phone (BLE). That's probably the best way to start for your "generation zero" product;)

[Tai]

Thanks for your reply. As I am new in this field. Do you have any example concerning BLE device with several connection links and they can have different GAP roles (Peripheral/Central)?

[endnode]

Have you read anything else in the field? Have you tried examples in Nordic nRF5 SDK? Have you tried any test app (like Nordic's nRF Connect or Light Blue) on mobile platforms and tried to set-up both scanner/advertiser at the same time + let the devices to connect? There are so many examples that if you don't see any it rather means you haven't spent even 30 minutes of trying...

If you really don't see any then just buy few nRF5x DK boards and set BLE relay example demo.