Future Strategies for AU915 and AS923 in Australia

Given we have systems with both AU915 and AS923 operating in Australia the question is, how do we best support these going forward? What is the best system configuration?

Returning to the frequency diagram you can see the following point

  • The most dominant form of AS923 in Australia is AS_920_923 which is at the bottom of the diagram
  • TTN AU915 is in FSB2 and its downlinks are transmitted on 923.9MHz which does not overlap with AS_920_923
  • AS_920_923 also does not overlap with systems running in FSB3, FSB4 or higher. Remember we share the band with other LoraWan systems, other IoT systems and general industrial systems that have nothing to do with Lora.

AS923 1and2

You will also see AS_923_925 aligns with FSB6 and so there is a proposal to move TTN from FSB2 to FSB6 and then every gateway can receive AU915 as well as AS923.

So what are the benefits and issues.

  • Every gateway will be able to receive AU915 and AS923 nodes. Nice!
  • Systems using AU915 loose the benefit of two frequency (duplex) operation as gateways when sending downlinks to AS923 nodes they will transmit on the same channel as the node → gateway uplink. (Refer above to see that difference between single frequency and dual frequency operation)
  • All the existing AS923 nodes which are in the AS_920_923 band will need reprogramming and move them to AS_923_925. I assume this will be the vast majority of these nodes as there are 293 gateways on AS_920_923 and only 30 on AS_923_925. If this is the case, why not reprogram them to work on AU915 FSB2?
  • This will also mean we need to move all existing AU915 systems from FSB2 to FSB6.
  • By being located in FSB6 we also have additional background noise from the downlink channels transmitted by LoraWan systems commissioned on FSB1, 2 and 3.
    These may not be TTN systems but other commercial systems, which by the way are likely to be heavily loaded. eg meter reading etc. Just because they don’t appear on the TTN map does not mean they don’t exist. (I have one myself)

From this I have concluded

  • Leave AS923 where it’s currently located as it will receive less interference and work better than moving it to AS-923_925
  • Leave AU915 where it is in FSB2
  • Continue to support existing AS923 systems - ie don’t remove existing gateways
  • The Australian TTN community promotes all new nodes should be installed on AU915
  • If a AS923 node is replaced (failure) then commission its replacement on AU915.
  • Gateways that are solely on AS923 are not a good idea.
  • All Gateways should be on AU915 and if a second head is installed it can be on AS923.
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