Re: uncalibrated general-purpose SDRs (was Re: Balancing BTS'es for handover)

Hi Domi, On Sun, Jan 13, 2019 at 11:17:33AM +0100, Tomcsányi, Domonkos wrote: Sure. I think it's not so much the size of the package, but mostly the software reconfiguration part for so-called "spectrum re-farming". This allows you to scale down the number of GSM carriers and scale up the number/width of LTE carriers without any on-site visits. When I said "general-pursose SDR" I was referring to a USRP-style or LimeSDR-style device. This means, basically 1) wide-band radio front-ends without band filters 2) IF or baseband filters that are muhc wider than GSM channels 3) all processing on general-purpose CPUs (as opposed to ASICs, DSPs or FPGAs) 4) no calibration of the RF output power over frequency and temperauture 5) no calibration of the Rx signal level over frequency and temperature 6) no clock that conforms even remotely to 3GPP accuracy requirements Of course not all of those topics are realted to the original discussion, and of course you can still use a general-purpose SDR as one element of a real-world base station. But then you have to add at least some of the missing elements I described above. For the calibration part: This could all be done in [open source software], if you have a signal generator with known/defined signal level. It would be a great project to define a calibration setup to determine calibration tables for Rx and Tx levels over (at least) frequency. OsmoBTS already has support for applying calibration tables on the transmit side, which were originally intended in case you add an external, non-linear-gain PA to a previously calibrated BTS. That could possibly be extended? For the receive side, no support exist. Regards, Harald -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)