Re: [Discuss-gnuradio] LoRa implementation

[Marcus Müller]

Hi Alberto,

I think that sounds like a fun project. The LoRaWan website is a little
vague till you find the specs [1], and even they do not cite a full PHY
document, but a quick patent search helped me find out that it's a Chirp
spread spectrum modulation, which led me to Semtech's Application Note
1200.22 .
Basically, take your symbol-to-be-transmitted, spread it by transforming
it to a series of up- or downchirps, for the LoRa modulation (there's
also a GFSK option for some bands as per the LoRaWan spec
So: First approach would probably be to take a good-SNR RX signal,
filter it to the channel BW; apply "quadrature demod"; a positive value
of phase difference would mean "up-chirp", a negative "down-chirp".
Slice as appropriate.
Altenratively: Apply correlation with chirp, detect whether same
"direction" or reversed (maybe something like: signal->FFT (lenght=chirp
duration*f_sample)->multiply_const (const = conj(dft(ideal chirp)),
vlen=fftlen) ->sum of vector->slicer))

Cheers,
Marcus

[1]
https://www.lora-alliance.org/portals/0/specs/LoRaWAN%20Specification%201R0.pdf
On 24.10.2015 12:35, Alberto Trentadue wrote:
> Hello
>
> I would like to know if anybody has attempted implementing a LoRa
> modulatiion using GNURadio.
>
> Thanks in advance for any indication.
>
> Best Regards
> Alberto Trentadue
>
>
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