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Maximum amount of nodes in Thread star topology

Aleksandr

Hello,

We are evaluating now a new project and I am struggling to get a feeling about one moment of Thread network and its particular implementation with nRF52840.

In our particular implementation we want to create a Thread star topology network with as maximum (300-400) possible end-nodes connected to one router. Router is a network coordinator/border router in the same time. 

The topology is fixed and created once during installation

One important fact that almost all of the nodes are in deep sleep mode and only maximum of 20-30 of them are active. 

My question is if it possible to create such a network? During a search through this forum I encountered the information that the maximum amount of nodes is limited by the amount of FLASH/ RAM on the router side. Is it true? Considering nRF52840 with 1Mb of Flash is it possible to maintain the information about such a big network? If no, can we extend use external flash to store the data? 

Thank you very much

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  • 0

    Hi,

    The theoretical maximum number of childrens for a single router in Thread is 511 nodes. The maximum number of supported devices will be limited by the RAM, as routers need to store information about nodes, and also buffer messages for sleepy end devices. The minimum required by the spec is 10 nodes.

    When you say that the devices will be in deep sleep mode, I assume that they will not be a part of the network in this state? In that case, I think it should be possible for a router to maintain 20-30 nodes, but I have not tested this myself. If you want all 300-400 nodes to be part of the network at all time (sleepy end devices), I do not think this will be possible.

    What will be the total network size, i.e., are you planning to have multiple routers with this amount of children?

    Best regards,
    Jørgen

  • 0 in reply to Jørgen Holmefjord

    Hi Jorgen,

    Thank you for the reply!

    We would like it to be a part of a network all time. The reason behind this is that we need a very short time from wake-up till starting of messages receiving from the router. I expect that when a node sleeps and is excluded from the network it would take larger time to re-establish connection again (like discovery/advertisement delay in BLE). We need a reaction time of 0.5s since a device wakes-up. 

    The network will be consisting of one router and 200-300 nodes. We don't want to have a mesh network because all devices will be battery powered. 

    But shouldn't it be possible to store the information about the network in the FLASH? I believe it will require additional SW effort? 

    Aleksandr   

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  • 0 in reply to Jørgen Holmefjord

    Hi Jorgen,

    Thank you for the reply!

    We would like it to be a part of a network all time. The reason behind this is that we need a very short time from wake-up till starting of messages receiving from the router. I expect that when a node sleeps and is excluded from the network it would take larger time to re-establish connection again (like discovery/advertisement delay in BLE). We need a reaction time of 0.5s since a device wakes-up. 

    The network will be consisting of one router and 200-300 nodes. We don't want to have a mesh network because all devices will be battery powered. 

    But shouldn't it be possible to store the information about the network in the FLASH? I believe it will require additional SW effort? 

    Aleksandr   

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