[Discuss-gnuradio] Current state of timestamping in USRP 1
What is the status of this? Isaac -- View this message in context: http://old.nabble.com/Current-state-of-timestamping-in-USRP-1-tp27457715p27457715.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] How to implement 64QAM?
Hi, I haven't looked at any of the QAM-related code in the GNU Radio baseline, but it should be possible to design a generic MQAM demodulator. In fact, you should be able to build a generic MQAM demodulator for a given constellation set. This, I've done before in Matlab. You start with an AGC, feed through an equalizer which is optimized for minimizing the phase error between recovered and truth symbols. Another way to look at it that for each symbol, find the symbol that matches closest to the constellation vector (thats your decode symbol) and then feed the error into the equalizer. I believe there is a way to form a generic carrier recovery and symbol recovery loops that can deal with generic MPSK style constellation of which MQAM is a part of. In fact, you could write a routine that can do anything from BPSK to 64QAM. my 2 cents, Isaac -- View this message in context: http://old.nabble.com/How-to-implement-64QAM--tp27396489p27405809.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Specs on OFDM demodulator for USRP 1,2
Hi, Does anyone have any specs on OFDM demodulator usage for the USRP 1 or 2 as in what kind of rates have you been able to process with it in real time? Thanks in advance, Isaac -- View this message in context: http://old.nabble.com/Specs-on-OFDM-demodulator-for-USRP-1%2C2-tp27343224p27343224.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Automatic Modulation Recognition
Eric, Im thinking I would just use a squaring, 4th power, 8th power, techniques and look for spectral peaks. What do you think? Isaac -- View this message in context: http://old.nabble.com/Automatic-Modulation-Recognition-tp26835383p26843607.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] ENERGY DETECTOR
I implemented an energy detector on the GNU Radio by using a GPU at my old job. We used an FFT based method which is not uncommon. What you do is FFT the data and then compute the PSD. Do this in overlapping blocks (e.g. 12.5%, 50%, etc). You could optionally use a window too. Then, with the PSDs, you create a long term average (LTA) and a short term average (STA). The STA might be 4 PSDs and the LTA might be 10 PSDs. Given the LTA, you set a threshold so many dB about it (e.g. 3dB). Call this threshold the noise riding threshold (NRT). Finally, to detect energy, given the NRT, you find places where the STA is greater than the NRT.that's where you have an energy. You can get a coarse center frequency and bandwidth by examining which PSD bins cross the NRT. Depending on your environment, you may find that you have lots of isolated, single-bin crossing due to noise. You can just filter these by saying an energy must have a minimum of 5 consecutive bins. Or, you can write an algorithm to combine bins. Say you have this, where C is a crossing: C_C_CC__ You can filter this to get: CC__ -Isaac abbasi wrote: HI ALL I'm trying to implement ENERGY DETECTOR using gnu radio. Is there any library or modules to help. Especially when implementing energy detection we need to estimate the awgn. I've searched in http://gnuradio.org/doc/doxygen/ but i cannot find any relative information. regards, -- View this message in context: http://old.nabble.com/ENERGY-DETECTOR-tp26709651p26709969.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
