search

Lora-net / LoRaMac-node

Reference implementation and documentation of a LoRa network node.
Other
1.88k stars 1.09k forks source link

Incorrect LoRa Bandwidth Value Limitation? #411

Closed gojimmypi closed 6 years ago

gojimmypi commented 6 years ago

There's a comment in sx1276.c claiming

// REMARK: When using LoRa modem only bandwidths 125, 250 and 500 kHz are supported

at this line: https://github.com/Lora-net/LoRaMac-node/blob/master/src/radio/sx1276/sx1276.c#L711

however the datasheet shows valid values for LoRa RegModemConfig1 (page 112) for all these bandwidth values:

image

and even this specification table on page 19 listed power for each LoRa receiver bandwidth value::

image

I was wondering where the limitation of 125, 250, and 500 kHz is documented?

Thanks

GuntherSchulz commented 6 years ago

@gojimmypi

This body of work in an implementation of LoRaWan, as specified by the LoRa Alliance, which dictates what physical communication parameters are used to be able to work with the Public LoRaWan Network.

As such, it implements what is needed to be compliant with their specification, and nothing more. More directly, any setting that are NOT in line with with the spec are non-compliant, and have no place in LoRaWan. Moreover, any non-compliant (read not-otherwise specified) physical setups will simply be ignored by the public WAN.

What you are referring to, is the physical capabilities of the Radio Transceiver in question, (which of course you are free to roll out for your own purposes in any way you see fit, provided it meets local regulations, of course). Just don't hope your custom setup will in any way be even seen by the LoRaWan.

As for the actual documentation you seek, simply grab the latest copy of the LoRaWan specification.

Hope this clears it up for you :)

nestorayuso commented 6 years ago

Yes, LoRa has bandwidths lower than 125KHz, but LoRaWAN doesn't use them. And this repository if for LoRaWAN

see https://github.com/Lora-net/LoRaMac-node/pull/264

gojimmypi commented 6 years ago

@nestorayuso and particularly @GuntherSchulz - thanks for taking the time for your detailed response. :) I was not aware that the LoRaWAN spec had this requirement. I've been working on the RadioHead drivers (LoRa, no WAN) when I found this repository.

Reference for future viewers:

http://www.airspayce.com/mikem/arduino/RadioHead/

https://www.rs-online.com/designspark/rel-assets/ds-assets/uploads/knowledge-items/application-notes-for-the-internet-of-things/LoRaWAN%20Specification%201R0.pdf

From page 40:

image