How does a radio telescope make a picture ? Sent from my iPhone Andrew Rich
On 14/11/2011, at 14:10, "Marcus D. Leech" <mle...@ripnet.com> wrote: > On 11/13/2011 11:00 PM, Josh Blum wrote: >> It looks like the ofdm blocks are using a fair amount of multiply and >> multiply const blocks: >> >>> gr-digital$ find -name "*ofdm*" | xargs grep mult >>> ./python/ofdm_sync_ml.py: self.mixer = gr.multiply_cc(); >>> ./python/ofdm_sync_ml.py: # The output theta of the correlator above >>> is multiplied with this correlation to >>> ./python/ofdm_sync_ml.py: self.mul = gr.multiply_ff() >>> ./python/ofdm_receiver.py: self.chan_filt = >>> gr.multiply_const_cc(1.0) >>> ./python/ofdm_receiver.py: self.sigmix = gr.multiply_cc() >>> ./python/ofdm_sync_pn.py: self.corr = gr.multiply_cc(); >>> ./python/ofdm_sync_pn.py: self.square = gr.multiply_ff() >>> ./python/ofdm_packet_utils.py: to get to a multiple of 8. >>> ./python/ofdm_packet_utils.py: # pad to multiple of 8 >>> ./python/ofdm_packet_utils.py: up being a multiple of 512 bytes when >>> sent across the USB. We >>> ./python/ofdm_packet_utils.py: is a multiple of 128 samples. >>> ./python/ofdm.py: @param pad_for_usrp: If true, packets are padded >>> such that they end up a multiple of 128 samples >>> ./python/ofdm.py: self.scale = gr.multiply_const_cc(1.0 / >>> math.sqrt(self._fft_length)) >>> ./python/ofdm_sync_pnac.py: self.corr = gr.multiply_cc(); >> I bet many of these multiply consts could be simplified out. But, doing >> little things like replacing the multiplier implementation with one >> optimized with the SIMD unit makes a big difference, especially on a arm >> where NEON>> FPU. >> >> So, there is a multiply and multiply const for floats that has been >> optimized in my gr-basic branch. You may want to try using those blocks >> instead. http://gnuradio.org/cgit/jblum.git/log/?h=gr_basic >> >> -Josh > The main transform in an OFDM transmitter, though, is an inverse FFT, and I > assume those blocks use the built-in FFTW implementation, > rather than doing their own. > > -- > Marcus Leech > Principal Investigator > Shirleys Bay Radio Astronomy Consortium > http://www.sbrac.org > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio