|
| From: | Brian Padalino |
| Subject: | Re: [Discuss-gnuradio] GMSK: GSM initial phase for a burst |
| Date: | Mon, 18 Jun 2007 16:14:07 -0400 |
On 6/18/07, Jeffrey Karrels <address@hidden> wrote:
Another quick question. I can now see that after the amplitude ramp up that there is a short section of negative phase movement (.7 radians clockwise) prior to the remaining counterclockwise rotations. Should I expect a full (-pi/2) to start off the burst? Is my sampling rate just not high enough to catch the remaining rotation? Any other suggestions?
GMSK has a certain level of ISI built into the waveform. 0.7 radians is about a pi/2 shift (0.2228 versus 0.25?) which would be pretty darn close. You can look at the inherent ISI within GMSK in a nice pretty graph in this PDF: http://www.ieee802.org/16/tg1/phy/contrib/802161pc-00_11.pdf You may want to filter your samples down to 1 sample per symbol and see if you get 3 dots close to each of your 4 constellation points (if you have already compensated for any phase rotations). Brian
| [Prev in Thread] | Current Thread | [Next in Thread] |