Hi, This doesn't look like a GSM signal. There some pictures of GSM spectrum captured with USRP on the internet. I don't have a link near my hands, but you can probably google them easily.
Regards, Alexander Chemeris. On Jun 3, 2011 4:21 AM, "TheOperator" <leo...@bluemail.ch> wrote: > > > Ben Wojtowicz wrote: >> Are you saying that you are seeing 4MHz wide signals? Or are you seeing >> ~200KHz wide signals seperated by 4MHz?I see about 200kHz wide signals >> spaced 4MHz. > > > Ben Wojtowicz wrote: >> If you are seeing ~200KHz wide signals spaced by 4MHz, these most likely >> are >> GSM signals. The spec states that the spacing between adjacent channels >> is >> 200KHz, but that does not mean that an operator will place all of their >> channels next to each other. In fact, it would be bad if they did this. >> Keep in mind that the spacing between channels is 200KHz, but the occupied >> bandwidth of a GSM signal is ~270KHz. This means that if GSM channels are >> placed next to each other, ICI will increase significantly. Typically >> what >> is seen is a very sparse scattering of channels across the band.Thanks for >> the explanation, this makes sense. The channels are not exactly 200kHz >> wide however (see screenshots), but according to the frequencies, they >> have to be GSM. > > I used this little system along with some GUI elements: > http://old.nabble.com/file/p31763653/gsm-900-blocks.png > > The resulting spectrum looks like this: > http://old.nabble.com/file/p31763653/gsm-900.png > > Such a peak has the following shape. Most of the power is distributed within > ~50kHz. Do these smaller peaks have a special meaning? > http://old.nabble.com/file/p31763653/gsm-900-zoomed.png > -- > View this message in context: http://old.nabble.com/GSM-spectrum%3A-Invisible-200kHz-carriers--tp31761278p31763653.html > Sent from the GnuRadio mailing list archive at Nabble.com. > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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