Re: [Discuss-gnuradio] No packet reception in higher modulation

[Josh Blum]

On 10/25/2011 01:48 PM, Nazmul Islam wrote:
> Hello,
> 
> I am running my codes in basic TX/RX with gnuradio-3.3.0 image. I am using
> benchmark_tx and benchmark_rx codes in the gnuradio-examples/python/digital
> folder to find packet loss for different modulation schemes (I believe that
> these files have been transferred to the gr-digital/examples/narrowband
> folder in the new image). When I run my the benchmark codes with dbpsk and
> dqpsk modulation, the receiver receives packets. However, when I run the
> codes with d8psk modulation scheme, the receiver just sits idle waiting for
> the packets but does not receive anything !
> 
>  I am giving the following commands in the benchmark programs:
> 
> ./benchmark_tx.py -f 2.4G -r 1M -e eth2 -m d8psk --tx-ampl 0.5
> 
> ./benchmark_rx.py -f 2.4G -r 1M -e eth2 -m d8psk
> 
> I am getting the following packet reception ratios for different modulation
> schemes:
> 
> dbpsk: 99%, dqpsk: 92%, d8psk: 0% !!
> 
> I expected to get less packets (higher packet loss) through d8psk modulation
> since it is transmitting at a higher data rate. But the receiver is not
> receiving anything at all !!
> 
> Your feedback will be highly appreciated.
> 

Have you observed frequency offset?

http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#I-have-two-USRPs-and-when-I-transmit-on-one-and-receive-on-the-other-at-the-same-frequency-I-get-an-offset

-Josh