On Sat, Jun 03, 2006 at 02:49:16PM +0800, 2 1 wrote: > Thanks for your working. > > I wonder if 1.28Msymbol/s (2.56Mbps for qpsk) is possible to be archieved > through costas loop. > I'm worry about the 32Mbyte/s of USB 2.0 interface may not be enough. > I've read the code from > http://aphex.media.mit.edu/wiki/tiki-index.php?page=BPSK (using costas loop) > and found that 8 samples are used to build a sinusoid wave at the baseband > level. Consindering complex sampling (4 bytes for one samle), the > maximum symbol rate is only 1M. If filter with over sampling is employed, > the data rate may be much lower. > > Right now, I'm thinking about using pilot seqence for doing carrier sync and > symbol sync together. I hope it works, but more experiments are needed.
The QPSK code works fine at 2 or more samples/baud. 2 Mbaud (4 Mbit/sec) should be doable, modulo CPU consumption. [We haven't measured the performance, or tried to do anything to make it run faster. Lots of room for improvement.] We're currently using a Costas loop to track the carrier followed by a complex M&M symbol timing block. Seems to work fine. We do whiten the transmitted signal to ensure lots of transitions. I'm giving a talk at USENIX today, and will get the rest of the QPSK code checked in by Monday. Eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
