Since you are going from B-PSK to Q-PSK modulation you may have a problem with spectral inversion. With B-PSK it won't matter, however with Q-PSK a +90 degree phase change will look like -90 degrees at the receiver.
You can invert the spectrum with the set_rx_freq command. Just set a negative IF frequency. src.set_rx_freq (0, -IF_freq) Hope that helps.... On Sun, 11 Nov 2007, Mohammad Hamed Firooz wrote: > > Hi > I hope at least one of the members of BBN group read this email. > I used BBN implementation of IEEE802.11b to receive packets from > commercial products. So I always use Barker code as the spreading key. > As it had been reported before, Their code works with 1Mbps and > doesn't work with 2Mbps. I cannot understand why. Since bandwidth of > DBPSK and DQPSK are the same, the problem is not because of low > sampling rate. I went precisely through thier code step by step and > everything seems to be correct. In fact, there is a little difference > between 1Mbps and 2Mbps modes. > To explain the problem clearly I copy and paste results of receiving > preamble and header of the short PLCP. You may know that for short > PLCP, preamble is sent by 1Mbps while Header is transmitted using > DQPSK (2Mbps) and both of them uses Barker code. > > Recieved (short) header! > signal: 0xBA > service: 0xE7 > length: 0x640D > crc: 0x388A > Calculated crc: 0x5112 > Recieved (short) header! > signal: 0xFF > service: 0xCB > length: 0x1A50 > crc: 0x2C29 > Calculated crc: 0x761C > Recieved (short) header! > signal: 0xF9 > service: 0x11 > length: 0x8340 > crc: 0x8B78 > Calculated crc: 0x5D2A > Recieved (short) header! > signal: 0x31 > service: 0x1F > length: 0xC729 > crc: 0xA902 > Calculated crc: 0x255D > Recieved (short) header! > signal: 0x04 > service: 0x09 > length: 0x9170 > crc: 0xBD57 > Calculated crc: 0x67E8 > > Almost never header is received correctly. I am looking for the reason > of the bug. As I mentioned before it is not because of low sampling > rate (the sampling rate is 8MSPs) > > regards, > hamed > > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
