On Fri, Apr 13, 2012 at 4:47 AM, 王伟华
<address@hidden> wrote:
Hi everyone,
I want to realize a BPSK modulation by using GRC to
transmit some bytes of information. Simulation result under a pure
software environment performs good. However, when I move to hardware
step with two USRPs connected with cable and 6dB attenuator(a simplex
scenario), less than half of the transmitted bytes can be received. I
think may be a synchronization problem occurs. Then I decide to do a
loopback setting (flow graph is attached and please check it) with one
USRP N210. This time, again, I cannot receive all the the transmitted
strings. Detailed information are shown below:
Ubuntu 10.04, GNU Radio software version 3.5.2.1, 2 samples/symbol,
sample rate 195.312K, both Gray coding and Differential encoding are
turned on, excess bandwidth 0.35, realtime scheduling, transmitted
strings 468Bytes, UHD gain 0dB, payload length 1(nothing received when
payload length equals 0) and central frequency at 1GHz.
Rx bytes: 82; 78; 79; 68; 51; (All 5 times shows very bad results, so I adjust some parameters)
I
turn off the Gray coding, keep the Differential encoding on; increase
samples/symbol to 5(5 samples/symbol gives the best receiving result);
Rx bytes: 418; 421; 417; 405; 415; Still I cannot receive all
transmitted bytes.I think synchronization is provided by packet encoder
already. What could be the possible reasons? I also try the 'run to
completion' option but nothing received. Why random results appear? I am
sure the cable and Ethernet cable have no problem.
Thanks a lot!
Kind Regards!
Wei
Try a payload length longer than 1. In addition, please use an attenuator of at least 20dB -- using only 6dB between the TX and RX will still provide enough energy to damage your daughterboard if you turn the gains up.
--n
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