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Tom Tsou tom at tsou.ccOn Mon, Jan 27, 2014 at 7:49 AM, Holger Hans Peter Freyther <holger at freyther.de> wrote: > On Sun, Jan 26, 2014 at 06:29:00PM -0500, Tom Tsou wrote: >> On Fri, Jan 24, 2014 at 7:29 AM, Holger Hans Peter Freyther >> <holger at freyther.de> wrote: >> > SDRs provide the greatest flexibility but unless you have specific >> > RF filters in your frontend you will not pass the harmonized norms >> > of the European Union for GSM. >> >> I think this statement is quite dated. > > Ah cool. Can you point me to papers/text showing how the n-th harmonic > is being removed from the spectrum? N-th harmonic of what? For the N200, The GSM baseband signal goes through a number of conversions and filtering stages on the host, FPGA, and DAC chip before reaching the converter at an interpolated rate of 400 Msps. There is 40 MHz of filtering on the WBX daughterboard, which removes aliasing from the DAC output. The older RFX900 daughterboard does have a filter on the front end, however, the performance is worse than the WBX in almost every measure. More recent devices are based on flexible integrated RF chips from Analog Devices and Lime Micro that were specifically designed for commercial 3G and 4G systems. I find it hard to believe that these SDR products are not capable of passing international compliance requirements for GSM. > The policy of FCC vs. European Union is quite different. There are more > norms that apply in Europe. Certain USRP products, notably the National Instruments variants, are CE tested and certified according to applicable European directives for which the product is sold. I am certainly not an expert in the area of compliance, but I assume this certification does not extend to operation of a GSM base station as the product is not sold as such. That brings up the point that for USRP type devices, the user is purchasing a piece of test equipment and not a BTS and is therefore responsible for meeting any subsequent application requirements. This contrasts with nanoBTS or sysmoBTS, which are fixed use GSM products and the burden of compliance lies with the supplier. For users who are concerned about compliance, the classification of the device is probably a larger issue than whether or not the device is technically capable of passing compliance norms. -TT