Network Depth

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What does the "network depth" number actually mean?
I mean the one you get back when you ask for neighbor information, like with +WNB.

It seems that I only get even numbers back and they have relative large numbers (6 on a 14-node network, for instance)

Could it be that those numbers are doubled???

Last Edited: Fri. Oct 16, 2015 - 02:17 PM
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When device joins a network it gets network depth of a parent and adds one to get its own depth. It is relatively meaningless parameter in a mesh network.

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Oh, I think it is an interesting number as it indicates the latency: We are using kind of a handshake/confirmation on application layer so each message has to go through the mesh and the confirmation back.

And in the current case I was assuming we had a depth of 2, maybe 3. But I see 6!

It might also help me with seeing the topology of the mesh. I know I shouldn't be concerned about it but as we go for longer-range meshes it is a great tool for diagnosing when some sensors are not getting the connection

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It does not indicate latency at all. It is just a number assigned at a join time.

NOTE: I no longer actively read this forum. Please ask your question on www.eevblog.com/forum if you want my answer.

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Baycity wrote:
Oh, I think it is an interesting number as it indicates the latency:

A node joins a network in a tree topology and communicates the data in a mesh topology.

So mesh topology will take care of the optimized route for delivering the data to the destination node.

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Yes, and the reason to choose a mesh in the first place was that there is no need to worry how data get routed.

But reality is different to the bench top or lab: People put nodes in funny places, transmission power is limited (and therefore range), even the mesh stack imposes some limitations in terms of number of direct neighbors and maximum mesh depth

It would really helpful for non-trivial systems to be able to see the connection graph including RSSi/LQI for each leg. That would make diagnosing so much easier

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You can do this from the application layer. Make each node send a list of its neighbors to the central node and recreate a network graph based on this information. Partial version of the same graph is shown by the WSNDemo/WSNMonitor application.

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Great! We were just discussing that idea here in the office and decided to give it a go.

Good to know that it is the way to do it :-)

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I have just read those list out of the nodes but I still can't figure out which path is used for transmission or what the topology is.
Have to say, all nodes are relatively close to each other, which could make the process a bit more difficult.

Just to make sure I do the right interpretation:
- The last number of each line of a "AT+WNB 3" command does give me the 'depth' of that node, means the coordinator should be 0, the nearest nodes 1, and so on?
- Are the nodes in the neighbor list necessarily direct neighbors or could they be more distant, means is there an RF link possible with no hops to that neighbor?
- My main interest is to know how marginal a node is in terms of mesh connection. Let's assume, there are 3 neighbors in the list. Can I just query the RSSI value to all 3 and assume the best connection will be used?

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Node depth is almost meaningless.

Neighbor list contains only direct neighbors.

RSSI does not relate to the best connection.

I don't think it is possible to figure out what you need using SerialNet.

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Ah, thanks. Yes, I did ask about the SerianlNet source to add commands which can provide me with that information.

But before I try to set this up, maybe there is a simple answer to this.
If I have a setup like this:

Coord ------ R1 -------- R2 -- R3

Then I would assume that
- R2 would see R1 and R3 as its neighbors
- The RSSI seen by R2 would be better towards R3 than toward R1
But what about LQI?
And is there any way to tell that R1 is closer to the coordinator and will be used for transmissions into that direction?

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Baycity wrote:
- R2 would see R1 and R3 as its neighbors
Correct.

Baycity wrote:
- The RSSI seen by R2 would be better towards R3 than toward R1
In an ideally isolated environment, yes. In general, no. RSSI is just a strength of a signal, it can be from a powerful noise source as well.

Baycity wrote:
But what about LQI?
In an ideally isolated environment LQI will be the same. In real life it will depend on how much noise is present on both ends of the channel.

Baycity wrote:
And is there any way to tell that R1 is closer to the coordinator and will be used for transmissions into that direction?
Stack takes care of discovering optimal routes.

NOTE: I no longer actively read this forum. Please ask your question on www.eevblog.com/forum if you want my answer.