End-device channel hopping algorithm

[yasiru-csiro (Yasiru)]

Based on the information available on the internet, LoRa end-device channel hopping is stated to be pesudo-random.

The end-device changes channel in a pseudo-random fashion for every transmission. The resulting frequency diversity makes the system more robust against interference.

1. Is it termed ‘pseudo-random’ because it considers all channels apart from the one it most recently transmitted on?

2. Is there a set algorithm it follows?

Thank you for your contribution.

[kersing (Jac Kersing)]

Have you read the LoRaWAN specification and the regional parameters document? (Keep in mind TTN currently uses version 1.0.2 of the specification, not version 1.1 on the public network)
And then searched for pseudorandom?
If do you know a limited device like a node is unlikely to have a full random generator?

1. No
2. No, if so it would not be pseudorandom.

[yasiru-csiro (Yasiru)]

As always, thank you for taking the time to respond.

I did read the LoRaWAN spec, and the quoted text in my original text was extracted from the LoRaWAN spec document. I think I might have missed the section in the regional parameters document regarding FHSS (under the US90-928 section), because I was looking for sections for Australia.

With regards to ‘pseudo-random number generator’, my understanding from reading the LoRaWAN specification was that it waso only used for frame transmissions (seeded with the device’s address).

Q: Is the difference between the standard uplink and the retransmission uplink that only the retransmissions are seeded with the device’s address?

I will do some further research on FHSS and ask further questions, if needed.

Thank you.