European FSK Channel

Channel Plan management
1

Hello all,

For our European sensors and gateway (running loraserver), we originally intended to use the same channel lineup that TTN uses. This lineup is as follows:

Uplink:

  1. 868.1 - SF7BW125 to SF12BW125
  2. 868.3 - SF7BW125 to SF12BW125 and SF7BW250
  3. 868.5 - SF7BW125 to SF12BW125
  4. 867.1 - SF7BW125 to SF12BW125
  5. 867.3 - SF7BW125 to SF12BW125
  6. 867.5 - SF7BW125 to SF12BW125
  7. 867.7 - SF7BW125 to SF12BW125
  8. 867.9 - SF7BW125 to SF12BW125
  9. 868.8 - FSK

Downlink:

  • Uplink channels 1-9 (RX1)

We have put our product through agency testing and the test lab is trying to get us certified to CEPT/ERC/REC 70-03 as a Class 1 device. However, I can not use the 868.8 MHz FSK channel to achieve this rating. I need to limit my transmissions to fall between 867.1 MHz and 868.5 MHz.

What happens if I simply disable this 868.8 MHz FSK channel in both the end nodes and in the gateway? We don’t need the high speed aspect. Will this work for us? Do I break anything by disabling the FSK channel?

Also, is it possible to still use FSK for one high-speed channel, but share the 868.3 MHz frequency to use FSK in addition to the LoRa modulation?

Thanks,
Jeremiah

2

In an SX130x based gateway (ie, all that presently exist) the FSK receive channel can be configured anywhere that fits fully in the bandwidth of one of the front end receivers. If it is a good idea or not depends a little on usage - while LoRa has a degree of rejection of FSK modulation, it’s not clear that FSK would do as well at rejecting co-channel LoRa interference. Of course the whole premise is the hope that true collisions will not be too frequent, it’s just that the LoRa channels and spreading factors have less mutual interference.

There’s no particular hardware limitation on transmit frequency, as long as it is generally within the designed band. Some versions of the packet forwarder like the current version of the Semtech reference code have a configurable allowed range and will enforce that, rejecting requests from a server to transmit outside of it, activating that could help your compliance efforts (though of course it is only a veto, it doesn’t mean the transmission would happen or be expected by the node on an allowed frequency instead)

If you look at various region configs you will see examples of the wideband lora channel and/or FSK channel being nestled among the other frequencies. GitHub - TheThingsNetwork/gateway-conf: The Things Network Master Gateway Configurations

3

Thanks for your reply Chris!

I believe I understand the possibilities regarding where I can place that FSK channel now. Do you have any insight on how that FSK channel is used in Europe? Furthermore, if I just disable the FSK channel, will I break any special functions like join, downlink, etc.?

Thanks again,
Jeremiah

4

Formally you want to read the applicable section of the LoRaWAN regional parameters document

From a quick glance it looks like the FSK channel is data rate 7, fast than DR6 which is SF7BW250 which is in turn faster than DR5 which is SF7BW125. DR7 and DR6 would be single-frequency given the gateway limitations.

It doesn’t look like nodes are told to use these during a join request, so likely a node would only get to these if an ADR algorithm told them to use DR6 or DR7.

So basically, if you don’t support these in the gateway you have to make sure server never commands them via ADR.