Re: [Discuss-gnuradio] GSM spectrum: Invisible 200kHz carriers?

[Ben Wojtowicz]

Operator,

Are you saying that you are seeing 4MHz wide signals?  Or are you seeing ~200KHz wide signals seperated by 4MHz?

If you are seeing 4MHz wide signals, they are not GSM.  There is most likely another technology being transmitted.

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.

Hope this helps,
Ben

On Jun 2, 2011 4:49 PM, "TheOperator" <address@hidden> wrote: