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
On Fri, Apr 13, 2012 at 4:47 AM, 王伟华 [email protected] wrote:
rate 195.312K, both Gray coding and Differential encoding are turned on,
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