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tapparelj / gr-lora_sdr

This is the fully-functional GNU Radio software-defined radio (SDR) implementation of a LoRa transceiver with all the necessary receiver components to operate correctly even at very low SNRs. This work has been conducted at the Telecommunication Circuits Laboratory, EPFL.
https://www.epfl.ch/labs/tcl/
GNU General Public License v3.0
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HackRF CRC issues #79

Closed radio-satellites closed 4 months ago

radio-satellites commented 7 months ago

Hi!

Thanks for the wonderful work!

I'm wondering about why my HackRF receiver nearly always produces wrong CRCs (sometimes correct ones, though), but my RTL SDR receives the same signal just fine.

I initially thought that the DC imbalance was the issue on the HackRF, so I tried receiving the same signal off to the side and centering it in GNURadio. However, this provided no measurable effect.

Another interesting observation I made is that this seems to affect only the long packets, the shorter ones get through with zero packet loss.

Would you have ideas on this @tapparelj?

Best,

Sasha

tapparelj commented 7 months ago

Hi @radio-satellites, Since you mention that only long packets suffer, it makes me think of an issue related to sampling frequency offset (SFO) as the more time passes, the more error you accumulate. In the current implementation, I assume that both the carrier frequency and the sampling frequency are generated using the same reference oscillator. This is used to get an estimate of the SFO based on the carrier frequency offset (CFO) estimated in the preamble. Maybe this assumption is not correct for the Hack-RF? If you add a Tag Debug after the _Framesync block, it should print the estimated CFO what value does it give?

radio-satellites commented 7 months ago

Hey @tapparelj !

Thanks for your reply!

I'm not quite sure whether or not a different reference oscillator is used in the HackRF.

So far I am using the integrated LoRa Rx block. Let me assemble the entire GnuRadio flow with those blocks and see what happens.

Thanks!

Sasha

tapparelj commented 4 months ago

Hello, I'll close this issue given that there has been no update since some time. Don't hesitate to reopen it if needed.