Bluetooth Mesh vs Thread in low power sensor network

[Mateusz Gancarczyk]

Hi, I’m working on low power wireless sensor network. I have a big dilemma in choose of wireless mesh solution. 
Maybe firstly, what i need:
1. Support for low power devices (for example temperature sensor).
2. Relay device - always on powered device with should extend range for low power sensor.
3. One central gateway, with concentrates data from all low power devices.
4. Wireless bootloader - for low power device and relay devices.
5. No single point of failure.
6. Good wireless range (the best will be use Bluetooth 5.0 long range mode).

Initially Bluetooth mesh and thread meet above condition, but when I got deep in these two technologies, i have many questions. For example:
1. In Bluetooth mesh Low Power Node can be only "connected" to only one Friend Node? So, if yes - when Friend Node fails or they not receiver signal from Low Power Node - signal from Low Power Node will lost. So in this case I cannot say that Bluetooth Mesh is no single points of failure.
2. Lastest SDK, not support friendly device. When new SDK will be relase. It's days/ few months?
3. Is this problem from point 1 exists in thread network? In: www.threadgroup.org/.../Thread_Technical_Overview.pdf
I found that Sleeping device automatically switches parent if it loses connectivity.
4. With sensor network have better low power performance?
5. In Bluetoth mesh, there is a easy to use provinsioning system. But what about Thread?

[Hung Bui]

Hi Mateusz, 

1. When friend node fails, the LPN by not able to talk to its friend will start looking for new friendship. What would be lost here would be the messages for the LPN that the friend node cached. 

If the Low Power node does not receive a response within the ReceiveWindow, it should resend the Friend Poll message. It is recommended to resend this message 3 times, which assures a good balance between reliability and power consumption.
If no response has been received to multiple Friend Poll messages before the PollTimeout timer expires, the friendship is terminated. The Low Power node may repeat the Low Power establishment operation.

(Section 3.6.6.4.2 in Mesh Spec v1.0)

2. It's coming in the next SDK, at least the LPN . Should be available by the end of this month. 

3. Yes it can find a new parents, but same as Friendship termination, the cached messages may be lost. 

4. It's hard to say pretty much depends on the operation of your network. It's more about which technology fit more into your application. Mesh is a flooding mesh when Thread is a routed mesh. Thread has IPv6 to each nodes.

5. In thread the router does the provisioning to join a node to the network. Each network has a leader to provision the routers. 

Regarding the low power option, there are many alternative to achieve low power besides the Low Power Node and Friendship solution.

- You can just put a normal node to sleep, it may miss packets send to it, but if it's simply a temperature sensor for example, we just need to receive data from it.

- Or you can make your device to advertise normal BLE advertising packet, and define a protocol in your normal mesh node to forward those packet into mesh, this is what we have in the Enocean energy harvesting light switch example.

- Another option is to configure your device as a GATT client proxy, to connect to a Proxy. This way you just need to maintain a normal BLE connection. 

[Mateusz Gancarczyk]

Thanks for great answer!

Two more question:

1. In the next SDK will be full example of LPN and friendship device?
2. Can I run Bluetooth Mesh with Bluettoth 5.0 Long Range ( x8 ) mode?

[Hung Bui]

Hi Mateusz,

1. It will be a full LPN example and a precompiled Friend node. 

2. It's theoriticaly possible to change PHY to run Mesh however for now it's not covered in the spec and you won't be able to qualify your product. So testing is ok , production not yet.