3 ms·

> The big issue with sub-GHz, of course, is bandwidth. Doesn't seem like a big issue for the IoT common case (switches, controls, alarms.)

fra 7y ago
Until you try to do an over-the-air firmware update :-).
- tw04 7y ago
  Why is that an issue? Presumably firmware updates are at best a monthly occurrence. Why do I care if it takes two days to push? Just make sure you have reliable resume and error checking.
  - anoncareer0212 7y ago
    "just"
  - oflannabhra 7y ago
    While this seems simple, most mesh network protocols use different routing protocols, network topography will be unique for every network, and even the nodes are ephemeral (especially if battery / mobile). All this means that your data throughput is highly unpredictable. Assuming that you have a border router (or similar persistent member of the network) who is in charge of disseminating your firmware over the mesh, you can either go with an algorithm that is unicast or multicast. Unicast can be tricky because you don't really want different firmwares running on the same network (especially if the firmware includes a networking stack update). It also takes a long time, because you have to send X bytes N times. Multicast can easily flood a network, even with rate limiting, because the amount of hops or rebroadcasts required can result in exponential growth in network activity. Simply extending the amount of time it takes is problematic. What if a device restarts? What if it drops off the mesh?You are definitely correct in that it is solvable. It is not incredibly simple, though.
MadWombat 7y ago
That is if you have a few devices. But if you have a mesh network of 200+ nodes exchanging health and routing information and at the same time trying to send and receive some actual data, bandwidth quickly becomes a rather important concern.
oflannabhra 7y ago
I also forgot to mention the other big issue with sub GHz: certification. Each country has their own frequency, from 800-900 MHz. Unless you buy a pre-certified package, you’re looking at expenses for certs probably higher that cost cost of development.
- onion2k 7y ago
  I think Amazon can afford the certification costs.
  - oflannabhra 7y ago
    > Amazon says it’ll publish the protocol so that other device makers can also integrate it into their devices. I doubt they will pay cert costs for other companies. Maybe they’ll provide a pre-certified package though.
    - dillonmckay 7y ago
      No, they will bill it like any other AWS service.

fra 7y ago

Until you try to do an over-the-air firmware update :-).

tw04 7y ago
Why is that an issue? Presumably firmware updates are at best a monthly occurrence. Why do I care if it takes two days to push? Just make sure you have reliable resume and error checking.
- anoncareer0212 7y ago
  "just"
- oflannabhra 7y ago
  While this seems simple, most mesh network protocols use different routing protocols, network topography will be unique for every network, and even the nodes are ephemeral (especially if battery / mobile). All this means that your data throughput is highly unpredictable. Assuming that you have a border router (or similar persistent member of the network) who is in charge of disseminating your firmware over the mesh, you can either go with an algorithm that is unicast or multicast. Unicast can be tricky because you don't really want different firmwares running on the same network (especially if the firmware includes a networking stack update). It also takes a long time, because you have to send X bytes N times. Multicast can easily flood a network, even with rate limiting, because the amount of hops or rebroadcasts required can result in exponential growth in network activity. Simply extending the amount of time it takes is problematic. What if a device restarts? What if it drops off the mesh?You are definitely correct in that it is solvable. It is not incredibly simple, though.

MadWombat 7y ago

That is if you have a few devices. But if you have a mesh network of 200+ nodes exchanging health and routing information and at the same time trying to send and receive some actual data, bandwidth quickly becomes a rather important concern.

oflannabhra 7y ago

I also forgot to mention the other big issue with sub GHz: certification. Each country has their own frequency, from 800-900 MHz. Unless you buy a pre-certified package, you’re looking at expenses for certs probably higher that cost cost of development.

onion2k 7y ago
I think Amazon can afford the certification costs.
- oflannabhra 7y ago
  > Amazon says it’ll publish the protocol so that other device makers can also integrate it into their devices. I doubt they will pay cert costs for other companies. Maybe they’ll provide a pre-certified package though.
  - dillonmckay 7y ago
    No, they will bill it like any other AWS service.