[Discuss-gnuradio] benchmark_rx is not receiving any packet for 8PSK modulation

[Nazmul Islam]

Hello,

I am working on the effect of adaptive modulation in packet loss. I am running my codes in USRP2 with XCVR2450 daughter-board and I am using UHD_003_001_002 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.

Now, 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. Let's say I am giving the following commands in the benchmark programs:

./benchmark_tx.py -f 2.4G -r 1M -e eth2 -m d8psk --tx-ampl 0.95  (I am using a very high transmitter power)

./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 !! Does it mean that the channel between the transmitter and the receiver is simply not good enough to transmit 3 bit per second per Hz? In other words, am I exceeding Shannon's capacity here?

Thanks,

Nazmul  


-- 
Muhammad Nazmul Islam

Graduate Student
Electrical & Computer Engineering
Wireless Information & Networking Laboratory
Rutgers, USA.