Need help understanding multiple Digi Mesh hopping!

I need help to understand Digi Mesh(hopping). I’m using xTend 900Mhz modules with Digi Mesh firmware 8x6x.

I’ve read the product manual for the xTend Digi Mesh but i still don’t understand a few things on how it works.

Lets say I have 10 by 10 area with 100 sensor nodes.
Each sensor will transmit a uni-cast transmission sensor data at the same time to an aggregate node or the node that will save the data. I guess each and every node will be a router, that it will assist other nodes to pass data to the aggregate node.

The manual says it uses routing algorithm using some reactive method AODV(ad-hoc on demand distance vector). I’m assuming that somehow it will create a reliable route to the aggregate node.

Lets say that 1 sensor node is at one end of the area and the aggregate node is on the opposite side. If the routing algorithm finds a “straight” and reliable route to the aggregate route it will use it and maybe hop 8 times but if not it will hop as many time as it needs to. Is this correct?

Or the sensor node transmits the data to its neighboring nodes which then those node assist to route the data to their neighbors and so forth until it reaches the aggregate node?

Will there be a problem with network becoming overly congested and data will reach not be able to reach the aggregate node due to bandwidth problems? Also every time a transmission successfully reaches the aggregate node a ACK is sent back ( assume it goes similar to how it is transmitted).

If anyone ever run into problems with big networks like the one I mention above feel free to leave a comment!!

Thanks for taking the time!


The Xtends does two things when it goes to transmit a data pack, First, it checks its neighbor table to see if the node it wants to send data to is within a 1 hop transmission. If it is not, it then sends a Rout Discovery which each node does the same check. That is, it looks at the destination address and says is this for me or within my neighbor table. If the answer is yes, a message is sent back with all possible routs. The transmitter then chooses the lowest path loss (Shortest) to transmit the data via and the data is transmitted.

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Can you expand on the Route Discovery? Does this Discovery route happen regularly or does it happen on a transmit only bases?

When should I be worried about the network becoming overly congested? Or when timing of a large network becomes an issue?

The timing is dependent on the application and what your timeout are set to in it.

The rout discovery only occurs on the first transmission to a new destination or to a destination that is not listed within the limited routing table of the transmitter.

Hello, I have the same doubt about 100 sensor making unicast to one node at the same time.
Hope someone with experience in that situation help us.

You can’t have more than one module send data at any give moment in time. You are going to need to have some variances between them or data collisions will occur.

Hello mvt, thanks for your response. Then I need to make, to achive high rate from many nodes, with my program of micro controller some mechanism to get the data sequentially.
Any mechanism to avoid collisions.

The xtend has in it the ability to do retries (RR) so I would let it use that function.