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Comment by femto | Hacker News Reader

In theory you can use a ($540) bladeRF in place of the ($2100) B200/210. It's got the same family 2x2 MIMO tx/rx chip in it as the B210. I say in theory, as I've been trying to get srsRAN to work with it, so far without success. It gets a response, but fails to establish the link. Has anyone managed to get srsRAN working with a bladeRF?

Others have mentioned Fabrice Bellard's LTE code, but (AFIAK) it's not freely available. Don't take this as a criticism. Bellard has done some great Free software and it shouldn't be expected that he will release everything as Free software.

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> Others have mentioned Fabrice Bellard's LTE code, but (AFIAK) it's not freely available. Don't take this as a criticism. Bellard has done some great Free software and it shouldn't be expected that he will release everything as Free software.

Also, I think that if Fabrice would release it as open-source, the pros/cons balance would be different compared to other projects (ffmpeg, qemu...) because

* very few people would be able to use and benefit this, considering that 1°/ you need proper (expensive) hardware, 2°/ anyway you cannot use licensed bands, 3°/ actually you can (mostly) also not use unlicensed bands without proper support from phones and without implementing the required band-sharing mechanisms from the regulation (e.g. listen-before-talk), and anyway LAA requires to use a licensed band as an anchor for signaling...

* it would have cancelled a source of revenue (today through Amarisoft)

Without knowing anything else about your setup my first guess would be synchronization issues. Do you have a GPSDO or some other means of providing a reference signal to your BladeRF?

Thanks for the idea. I'll give it a go. srsRAN includes carrier frequency offset estimation and compensation, but it can't hurt to assume it's got a problem there.

1) the LTE base clock has a giant denominator when using a LimeSDR with it's on-board crystal. A crystal for the LTE base clock is single-digit cost and fixes this (you can even set it up as a VCO to use as a fractional PLL off of some more-stable reference (10MHz GPSDO should be easiest, but it could also directly GPSDO the LTE crystal for mildly better performance at a big effort expense)), as the stability is to keep multiple eNodeB's OFDM symbols (and more importantly, TDMA slots) aligned so they can collaborate for broadcasts and get by with using the same spectrum on overlapping cells.

2) I'd worry much more about near end cross talk without a specially tuned diplexer that splits TX/RX of FDD LTE channels. Try a TDD band your hardware supports to try.

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