Beamforming in Pothos


I am new in SDR and I would like to do Beamforming for a LoRa gateway to extend even more the communication range. I’m using LimeSDR-USB.

I have read some methods of beamforming but only the theory. I found there are some projects about this topic but using GNU Radio ( can’t find the source code also )

It’s quite complicated for me doing it from scratch. So can anyone suggest me the Roadmap to accomplish this project ? How could I implement an algorithm in Pothos ? Do I need to touch on the FPGA or Programming in C++/Python is enough ? Some similar project that I can take a look on ?

Thank you so much

Guessing @g4guo may be able to point you at some recommended reading.

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I think it is a case of Google is your friend. Beam forming is a very hot topic for 5G so there is plenty
of material about. Is beam forming the best solution to your problem or might it be simpler to have a number
of small Yagi-Uda antennas pointing in different compass directions and switch between them?
There is not much you can do with just 2 channels, the ‘beam’ will have low gain and multiple sidelobes.
If you have interference it might be better to use the ‘beam forming’ to steer an antenna null in the
direction of the interferer.

You shouldn’t need to touch the FPGA code unless you are trying to beam form very wide bandwidth

Sorry I am not much help.

  • Charles
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Thank you so much for your information @g4guo . I will try to do it first with 2 channels (definitely there are things that I can learn from) and after will see how to implement with more antennas :smiley:

@dienhoa @andrewback

I was going to suggest you got a copy of “Digital Beamforming in Wireless Communications” by Artech House but then I looked at the used price on Amazon only to find they are now selling for x4 the price I paid for my copy!

It is a good basic overview of the subject.

I am still at the antenna topology stage. I will only have 8 antennas centred on 437 MHz.

There are also some other threads on this forum concerning MIMO operation and the issues with
sample alignment which you need to read. I plan to use a low power reference transmitter and do
system calibration in software.

  • Charles

@g4guo @andrewback
I have read about the issues of sample alignment but is it involved when I use Pothos to simutaneously use 2 Rx ?

Judging by the MIMO thread I read yes, it can be out by 1 sample on random basis.

  • Charles

Suspect @IgnasJ or @joshblum may be able to comment on this.

Because I see in Pothos there is one block called “Channel Aligment”
It indicates “Use this block in conjunction with multiple SDR source blocks to maintain channel alignment”. Maybe it is used to fix this problem ?

I’ve been wanting to try different methods of beam forming, one of them being this “cheap” method:

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